sync oslo service to fix SIGHUP handling

this is a sync of the oslo service code to fix a bug found in
the sighup handling. Previously it was not possible to use
devstack's unstack.sh because the service module would always
restart under a SIGHUP, not only when the process was running as
a service. SIGHUP on a non-detached process should act like
SIGTERM. This change fixes that.

Change-Id: Ib260d82519fde5c5cb24a2c0c8a7cccd0b96b84f
Related-Bug: #1263122
Merge "sync oslo service to fix SIGHUP handling"