Fix race condition for FakeDatasource
Fix race condition for FakeDatasource

Sometimes tests fail locally because the update_from_datasource()
method is called on FakeDatasource, but that method isn't implemented.

Change-Id: If09c0dd5cb5dcc5562568e031014481f548eb952

ekcs/congress,ramineni/my_congress,openstack/congress,ramineni/my_congress,ramineni/my_congress,ramineni/my_congress,ekcs/congress,ekcs/congress,ekcs/congress,openstack/congress