gnocchi: fixes stable/2.2 branch gate breakage
gnocchi: fixes stable/2.2 branch gate breakage

Gnocchi stable/2.2 is Mitaka release it
should run on trusty.

Change-Id: Ibf783a8f1f5f6a3ed6a2dbb1f03fd47725ed24c3

openstack-infra/project-config,openstack-infra/project-config,Tesora/tesora-project-config,Tesora/tesora-project-config