Ceilometer uses gnocchi as the default backend. Also we use
gnocchi based aodh alarms in tests.
gnocchi seems unmaintained with last commit a year or so ago and
does not look like the openstack telemetry team is involved in
that project.
It's better to disable the services and tests in heat to avoid
broken gate like last time, where we fixed it by banning latest
pecan release[1] that does not work with python-gnocchiclient.
[1] https://review.opendev.org/#/c/746261/
Change-Id: Id2ffdf6b9d342e800bab4a94ec46742228361ee8
9efbec6cd9