Remove sleep from service group db and mc tests

Before servicegroup.test_db_servicegroup and test_mc_servicegroup used
eventlet to put the test to sleep and waited for the service to run its
periodic _report_state instead of using timeutils and explicitly calling
_report_state.
 By switching to a timeutils fixture The following tests, are removed
from the list of top 10 lowest tests:

nova.tests.servicegroup.test_db_servicegroup.DBServiceGroupTestCase.test_DB_driver
nova.tests.servicegroup.test_mc_servicegroup.MemcachedServiceGroupTestCase.test_memcached_driver

Change-Id: I091a9975cc7e4fccb26700359d1e3b5c165034d3
Merge "Remove sleep from service group db and mc tests"