Refactor tests.unit.utils:FakeDB.reset
Refactor tests.unit.utils:FakeDB.reset

glance.tests.unit.utils:FakeDB uses glance.db.simple.api which has
already implemented reset() functionality, the redundant code in
FakeDB should be removed.

Change-Id: I140e932e9cc531900cee503e20d3549549b13d27
Closes-Bug: #1264204

scripnichenko/glance,takeshineshiro/glance,sigmavirus24/glance,klmitch/glance,sigmavirus24/glance,rajalokan/glance,ozamiatin/glance,klmitch/glance,dims/glance,stevelle/glance,paramite/glance,openstack/glance,paramite/glance,ozamiatin/glance,openstack/glance,akash1808/glance,JioCloud/glance,openstack/glance,darren-wang/gl,redhat-openstack/glance,darren-wang/gl,takeshineshiro/glance,dims/glance,wkoathp/glance,jumpstarter-io/glance,JioCloud/glance,scripnichenko/glance,wkoathp/glance,rajalokan/glance,redhat-openstack/glance,akash1808/glance,tanglei528/glance,jumpstarter-io/glance,saeki-masaki/glance,vuntz/glance,kfwang/Glance-OVA-OVF,vuntz/glance,tanglei528/glance,saeki-masaki/glance,stevelle/glance,kfwang/Glance-OVA-OVF