Temporarily add gnocchiclient to acceptance test

Temporarily add gnocchiclient to acceptance test

Currently CI is blocked because the ceilometer package in RDO does not
properly have gnocchiclient as a depedency. It has been determined
upstream that this dependency is not correct. So as a temporary solution
until the correct upstream fix lands, we need to pull in the
gnocchiclient in the acceptance test. This did not get caught by the
p-o-i testing because we install gnocchi with ceilometer in the
scenario.  This should be reverted one the package lands with the fix
for LP#1621384

Change-Id: I45db3cbc593d5f57e599513a0aba843c3d5da414
Related-Bug: #1621384