Fuel psycopg2.InternalError on deleting cluster wit API

[Georgy Dyuldin]

Detailed bug description:
 Fuel client raises HTTPError: 400 Client Error: Bad Request for url: http://10.109.19.2:8000/api/v1/clusters/2/ ((psycopg2.InternalError) current transaction is aborted, commands ignored until end of transaction block
[SQL: 'UPDATE tasks SET message=%(message)s, progress=%(progress)s WHERE tasks.id = %(tasks_id)s'] [parameters: {'progress': 100, 'message': "(psycopg2.extensions.TransactionRollbackError) deadlock detected\nDETAIL: Process 5948 waits for ShareLock on transaction 3670; blocked by process 6743.\nProcess 6743 waits for ShareLock on transaction 3669; blocked by process 5948.\nHINT: See server log for query details.\n [SQL: 'SELECT clusters.id AS clusters_id, clusters.mode AS clusters_mode, clusters.status AS clusters_status, clusters.net_provider AS clusters_net_provider, clusters.ui_settings AS clusters_ui_settings, clusters.name AS clusters_name, clusters.release_id AS clusters_release_id, clusters.replaced_deployment_info AS clusters_replaced_deployment_info, clusters.replaced_provisioning_info AS clusters_replaced_provisioning_info, clusters.is_customized AS clusters_is_customized, clusters.fuel_version AS clusters_fuel_version, clusters.components AS clusters_components, clusters.extensions AS clusters_extensions \\nFROM clusters \\nWHERE clusters.id = %(param_1)s FOR UPDATE'] [parameters: {'param_1': 2}]", 'tasks_id': 13}])

Steps to reproduce:
 Create new cluster with fuel client (VLAN network, without nodes)
 Enable ironic
 Check baremetal network settings
 Disable ironic
 Check that no baremetal network on networks tab
 Enable ironic
 Check baremetal network settings
 Delete cluster

Expected results:
 Cluster deleted successful

Actual result:
 Fuel returns above exception on deleting cluster

Reproducibility:
 About 5-10% of cases

Description of the environment:
 MOS 9.1 snapshot #327