_carbonara: stop heartbeat thread on stop()
_carbonara: stop heartbeat thread on stop()

Change-Id: Ie79f6dd5ff7a11e964fdf049ccfdc642cef89e5a
Closes-Bug: #1586443

leandroreox/gnocchi,gnocchixyz/gnocchi,sileht/gnocchi,sileht/gnocchi,gnocchixyz/gnocchi,leandroreox/gnocchi