Replace using tests.utils part3

It is the last step to replace using tests.utils with
stack.common.test.
In this patch database tests is changed for using
openstack.common.test and added needed fixtures in test classes.

Blueprint: common-unit-tests
Change-Id: I9b360f9a8dc72bc3fb697e571555775bde10ef61
Merge "Replace using tests.utils part3"