Replace occurences of 'test_tenant' with 'test-tenant' in tests

tenant_id will now be consistent among all resources created.
This is important when getting or listing resources by tenant_id.
Most resources are created under the 'test-tenant', while
metering and security groups were created under 'test_tenant'.

Closes-Bug: #1335821
Change-Id: Ifde22814ab5c302e751f2102f6fd7ef52c932126
Merge "Replace occurences of 'test_tenant' with 'test-tenant' in tests"