The default value for heartbeat_in_pthread has been reverted in
oslo.messaging to False [1] and backported back to Yoga.
At the moment this setting brings intermittent issues during live
migrations of instances and some other operations. So makes sense
to align it with default value.
[1] https://review.opendev.org/c/openstack/oslo.messaging/+/852251
Change-Id: I5601726095ff19620de2d87220efad191cf7cb6d
(cherry picked from commit d40f5a4725)