Fix devstack for gnocchi collector
Fix devstack for gnocchi collector

The gnocchi collector can't work when cloudkitty is deployed by devstack.
Because the gnocchi repository has been changed.

Change-Id: Id035524b77f32ed971f3d51f3c79f9b44241f7a1
Closes-bug: #1733734

stackforge/cloudkitty,openstack/cloudkitty,stackforge/cloudkitty,openstack/cloudkitty