Check domain_id with equality in assignment kvs

It was noticed in https://review.openstack.org/70816 that the kvs
assignment backend was using a contains check instead of an equality
check which comparing domain_ids.

Change-Id: Ib1b51298c8171151844caaa5ab694117e68374e7
Cleanup ldap tests (mox and reset values)

When running concurrent test workers, the structure used to test
the instantiation of the FakeLdap handler was relying on mox. In
some cases the test structures were not reset during teardown.

The test cases were not clearing out the _HANDLERS in the common
ldap module. This has been corrected with an addCleanup and moving
the setUp logic to the BaseLDAPIdentity class instead of the
LDAPIdentity class.

Change-Id: I2976774dabeb2b9196b3f25c02838bf4c4688d94
Merge "Check domain_id with equality in assignment kvs"
Merge "Cleanup ldap tests (mox and reset values)"