Don't run store tests without a store!
Don't run store tests without a store!

Store tests reuse a base test case which defines relevant test
functions. However, the base test case should never run independently,
only in a subclass, because it has no store to test.

Somehow, this issue only occurs if you run tox -- --tests
glance/tests/functional/store

Change-Id: I5d8d26ba68d034fb8e94e5408a757d9869825285

akash1808/glance,darren-wang/gl,stevelle/glance,vuntz/glance,openstack/glance,wkoathp/glance,sigmavirus24/glance,wkoathp/glance,openstack/glance,jumpstarter-io/glance,klmitch/glance,JioCloud/glance,SUSE-Cloud/glance,takeshineshiro/glance,dims/glance,scripnichenko/glance,paramite/glance,ntt-sic/glance,ozamiatin/glance,rickerc/glance_audit,JioCloud/glance,ozamiatin/glance,rajalokan/glance,jumpstarter-io/glance,citrix-openstack-build/glance,redhat-openstack/glance,sigmavirus24/glance,takeshineshiro/glance,kfwang/Glance-OVA-OVF,saeki-masaki/glance,citrix-openstack-build/glance,scripnichenko/glance,kfwang/Glance-OVA-OVF,saeki-masaki/glance,stevelle/glance,SUSE-Cloud/glance,vuntz/glance,dims/glance,ntt-sic/glance,rickerc/glance_audit,cloudbau/glance,klmitch/glance,cloudbau/glance,openstack/glance,akash1808/glance,paramite/glance,rajalokan/glance,tanglei528/glance,tanglei528/glance,darren-wang/gl,redhat-openstack/glance