Remove glance_store specific unit tests
Remove glance_store specific unit tests

TestStoreAddToBackend contains a set of tests that should belong to
the glance_store. Recently, these tests were about to break
glance as they mocked internal methods. Those mocks were
removed in commit eab1567d48a18fa968c7b66c3641dd037da1f84e.

The tests are added back to glance_store in
change https://review.openstack.org/#/c/273786.

Depends-On: I688629d37e9146aef33fbc9bb6fd8780521e06ab
Change-Id: Ic67826a4d02cb30cc429a3d4abc46d6ca96f31ad

openstack/glance,rajalokan/glance,rajalokan/glance,stevelle/glance,klmitch/glance,openstack/glance,dims/glance,openstack/glance,dims/glance,klmitch/glance,stevelle/glance