Include cisco plugin in migration plugins with ovs

Currently we have many migration files with missing cisco
plugin in migrate_plugin when ovs is included.This
causes missing tables when cisco plugin is enabled
and migration is run. This fix should automatically
include the cisco plugin if ovs is detected in the
migrate_plugins.

Change-Id: I4dedfbafe9b431e85255d5427766e22eed09ee5e
Closes-Bug: #1292114
Migrate data from cap_port_filter to vif_details

There was introduced a new column vif_details for ml2_port_binding table
and dropped cap_port_filter column. Data was lost during the migration
causing no data in vif_details.

This patch transforms data from cap_port_filter to vif_details column as
a part of db migration. MigrationContext.execute() calls underlaying
methods depending whether migration is online or offline therefore data
are migrated in offline migration too.

Partial-bug: #1235149
Change-Id: Icc5dc6e8221a542f5190d0222ac4d10197d15ac1
BigSwitch: Move attr ref after error check

Change in Big Switch server manager module:
Moves an attribute reference to a line after
the error check that validates the object is
not None.

Closes-Bug: #1298699
Change-Id: I5f9abf3b456d5066e90c05bc6b3aa5adcecb7943
Merge "BigSwitch: Move attr ref after error check"
Merge "Include cisco plugin in migration plugins with ovs"
Merge "Migrate data from cap_port_filter to vif_details"