We meet same error, manila-6.0.1 with Generic driver.
Share server never get created succesfully.

+--------------------------------------+--------+------+-------------+--------+-----------+--------------------+-----------------------------------------+-------------------+
| ID                                   | Name   | Size | Share Proto | Status | Is Public | Share Type Name    | Host                                    | Availability Zone |
+--------------------------------------+--------+------+-------------+--------+-----------+--------------------+-----------------------------------------+-------------------+
| 68f90beb-5222-4e03-a9db-2f28cb811984 | share1 | 1    | NFS         | error  | False     | default_share_type | xxxxxxxxxxxxxxxxxxxxxxx@generic#GENERIC | nova              |
+--------------------------------------+--------+------+-------------+--------+-----------+--------------------+-----------------------------------------+-------------------+

2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters [req-5907456c-ebf7-4895-9e48-613943ec7a98 7f25360ba6bb4480b2ab153da41e6a5d 504bf34e67784e258981a782add8e995 - - -] DBAPIError exception wrapped from (pymysql.err.IntegrityError) (1048, u"Column 'value' cannot be null") [SQL: u'INSERT INTO share_server_backend_details (created_at, updated_at, deleted_at, deleted, `key`, value, share_server_id) VALUES (%(created_at)s, %(updated_at)s, %(deleted_at)s, %(deleted)s, %(key)s, %(value)s, %(share_server_id)s)'] [parameters: {'deleted': 'False', 'created_at': datetime.datetime(2019, 6, 14, 6, 15, 21, 468474), 'updated_at': None, 'value': None, 'share_server_id': '3f8054a5-0ce4-4e0b-9108-9f1295c4bf68', 'key': 'subnet_id', 'deleted_at': None}] (Background on this error at: http://sqlalche.me/e/gkpj): IntegrityError: (1048, u"Column 'value' cannot be null")
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters Traceback (most recent call last):
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/base.py", line 1193, in _execute_context
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters     context)
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/default.py", line 507, in do_execute
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters     cursor.execute(statement, parameters)
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/cursors.py", line 170, in execute
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters     result = self._query(query)
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/cursors.py", line 328, in _query
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters     conn.query(q)
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/connections.py", line 516, in query
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters     self._affected_rows = self._read_query_result(unbuffered=unbuffered)
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/connections.py", line 727, in _read_query_result
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters     result.read()
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/connections.py", line 1066, in read
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters     first_packet = self.connection._read_packet()
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/connections.py", line 683, in _read_packet
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters     packet.check_error()
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/protocol.py", line 220, in check_error
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters     err.raise_mysql_exception(self._data)
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/err.py", line 109, in raise_mysql_exception
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters     raise errorclass(errno, errval)
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters IntegrityError: (1048, u"Column 'value' cannot be null")
2019-06-14 14:15:21.469 5830 ERROR oslo_db.sqlalchemy.exc_filters
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters [req-5907456c-ebf7-4895-9e48-613943ec7a98 7f25360ba6bb4480b2ab153da41e6a5d 504bf34e67784e258981a782add8e995 - - -] DBAPIError exception wrapped from (pymysql.err.IntegrityError) (1048, u"Column 'value' cannot be null") [SQL: u'INSERT INTO share_server_backend_details (created_at, updated_at, deleted_at, deleted, `key`, value, share_server_id) VALUES (%(created_at)s, %(updated_at)s, %(deleted_at)s, %(deleted)s, %(key)s, %(value)s, %(share_server_id)s)'] [parameters: {'deleted': 'False', 'created_at': datetime.datetime(2019, 6, 14, 6, 15, 21, 491501), 'updated_at': None, 'value': None, 'share_server_id': '3f8054a5-0ce4-4e0b-9108-9f1295c4bf68', 'key': 'router_id', 'deleted_at': None}] (Background on this error at: http://sqlalche.me/e/gkpj): IntegrityError: (1048, u"Column 'value' cannot be null")
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters Traceback (most recent call last):
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/base.py", line 1193, in _execute_context
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters     context)
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib64/python2.7/site-packages/sqlalchemy/engine/default.py", line 507, in do_execute
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters     cursor.execute(statement, parameters)
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/cursors.py", line 170, in execute
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters     result = self._query(query)
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/cursors.py", line 328, in _query
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters     conn.query(q)
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/connections.py", line 516, in query
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters     self._affected_rows = self._read_query_result(unbuffered=unbuffered)
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/connections.py", line 727, in _read_query_result
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters     result.read()
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/connections.py", line 1066, in read
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters     first_packet = self.connection._read_packet()
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/connections.py", line 683, in _read_packet
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters     packet.check_error()
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/protocol.py", line 220, in check_error
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters     err.raise_mysql_exception(self._data)
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters   File "/usr/lib/python2.7/site-packages/pymysql/err.py", line 109, in raise_mysql_exception
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters     raise errorclass(errno, errval)
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters IntegrityError: (1048, u"Column 'value' cannot be null")
2019-06-14 14:15:21.491 5830 ERROR oslo_db.sqlalchemy.exc_filters
2019-06-14 14:15:21.528 5830 ERROR manila.share.manager [req-5907456c-ebf7-4895-9e48-613943ec7a98 7f25360ba6bb4480b2ab153da41e6a5d 504bf34e67784e258981a782add8e995 - - -] Creation of share instance 364f7eb9-11a2-4f2b-9376-d9ac7639f4dc failed: failed to get share server.: BadRequest: The requested availability zone is not available (HTTP 400) (Request-ID: req-e4d3f653-229f-47ef-a498-7300cf87e45c)