Use real mocking in unit tests test_cname_lookup
Use real mocking in unit tests test_cname_lookup

Replacing function without mocking creates weird behaviors as the results
of the tests sometimes depends on the order of the execution. Use real
mocking to avoid such behaviors.

Example: using real mock showed that test test_host_is_storage_domain was
wrong because it was not "reseting" the lookup_cname function at the
beginning of the test.

Change-Id: Ibc60697c9c850e6e3a108f0d906e8906c3f53ced

smerritt/swift,tipabu/swift,notmyname/swift,matthewoliver/swift,swiftstack/swift,nadeemsyed/swift,clayg/swift,clayg/swift,tipabu/swift,nadeemsyed/swift,psachin/swift,matthewoliver/swift,clayg/swift,openstack/swift,redbo/swift,swiftstack/swift,redbo/swift,smerritt/swift,psachin/swift,matthewoliver/swift,matthewoliver/swift,notmyname/swift,clayg/swift,nadeemsyed/swift,notmyname/swift,nadeemsyed/swift,swiftstack/swift,psachin/swift,psachin/swift,tipabu/swift,openstack/swift,smerritt/swift,openstack/swift,tipabu/swift,openstack/swift,notmyname/swift,smerritt/swift