fix the qpid_heartbeat option so that it's effective
fix the qpid_heartbeat option so that it's effective

The 'hearbeat' typo caused this setting to be ineffective.
This bug has been present since the initial nova qpid implementation.

Fixes bug: 1030430
Change-Id: Ibb9d7484b9d11a6904cc9e2a8dde6d9164ee05b1

JioCloud/oslo-incubator,JioCloud/oslo-incubator,JioCloud/oslo-incubator