move common sql test helpers to base class
move common sql test helpers to base class

the few methods moved are generally helpful for any SQL upgrade
test, move them to the base class.

Change-Id: I5604569c766daa4c3ac9c24e64f5e4a793479d3a

openstack/keystone,rajalokan/keystone,rajalokan/keystone,rajalokan/keystone,mahak/keystone,mahak/keystone,ilay09/keystone,ilay09/keystone,ilay09/keystone,openstack/keystone,mahak/keystone,openstack/keystone