Fix gnocchi gate error
Fix gnocchi gate error

Gnocchi team removed etc/gnocchi folder in favor of
a custom command calling oslo-config-generator [0]

[0] https://review.openstack.org/#/c/419064/

Change-Id: I250f3bec7c1bba0018acc6251c54e0026b1dcae8

intel-onp/kolla,GalenMa/kolla,stackforge/kolla,coolsvap/kolla,intel-onp/kolla,nihilifer/kolla,stackforge/kolla,coolsvap/kolla,mrangana/kolla,nihilifer/kolla,GalenMa/kolla,coolsvap/kolla,stackforge/kolla,rahulunair/kolla,openstack/kolla,openstack/kolla,mrangana/kolla,rahulunair/kolla