Don't mock internal method of ceilometerclient
Don't mock internal method of ceilometerclient

Let's not mock an internal method, which may change again and
mock SessionClient.request() instead.

Change-Id: I59dbf70ce4610eb8e000f8f7a36f1e0af356c4b8
Related-Bug: #1659652

noironetworks/heat,noironetworks/heat,openstack/heat,openstack/heat