Allow for invalid packet sequence in keepalive

[Amrith Kumar]

In the SQLAlchemy keep_alive class, MariaDB is failing as pymysql reports an invalid packet sequence. MariaDB seems to timeout the client in a different way than MySQL and PXC, which manifests itself as the aforementioned invalid sequence. It is now handled as a special-case exception.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/362347
Committed: https://git.openstack.org/cgit/openstack/trove/commit/?id=bd761989eead77eead58c91ccb30fcb53d7a5c5d
Submitter: Jenkins
Branch: master

commit bd761989eead77eead58c91ccb30fcb53d7a5c5d
Author: Peter Stachowski <email address hidden>
Date: Mon Aug 29 19:47:47 2016 +0000

    Allow for invalid packet sequence in keepalive

    In the SQLAlchemy keep_alive class, MariaDB is failing
    as pymysql reports an invalid packet sequence.
    MariaDB seems to timeout the client in a different
    way than MySQL and PXC, which manifests itself as the
    aforementioned invalid sequence. It is now handled
    as a special-case exception.

    With this fix, the MariaDB scenario tests now pass.

    The scenario tests were also tweaked a bit, which aided
    in the testing of the fix. 'group=instance' was created,
    plus instance_error properly interleaved with
    instance_create. _has_status now calls get_instance with
    the admin client so that any faults are accompanied by
    a relevant stack trace. Cases where the result code
    was being checked out-of-sequence were removed, and explicit
    calls to check the http code for the right client were added.

    The replication error messages for promote and eject were
    enhanced as well to attempt to debug spurious failures.
    One of those failures was 'Replication is not on after 60 seconds.'
    This was fixed by setting 'MASTER_CONNECT_RETRY' in the mariadb
    gtid replication strategy as was done in:
    https://review.openstack.org/#/c/188933

    Finally, backup_incremental was added to MariaDB supported
    groups and cleaned up elsewhere.

    Closes-Bug: #1621702
    Change-Id: Id6bde5a34e1d79eece3084f761dcd153c38ccbad