Add monitoring for object-replicator logs disappearing
As noted in lp#1691570, there is an issue with storage I/O during
coro-thread cleanup that affects the swift-object-replicator's ability
to complete replication successfully. This is most easily witnessed by
the lack of the every 5 minute replicated percentage complete messages
that should come from the swift-object-replicator daemon to syslog.
This patch monitors for and alerts on the condition of the "replicated"
line missing from syslog within the past 15 minutes.
The mock third party library was needed for mock support in py2
runtimes. Since we now only support py36 and later, we can use the
standard lib unittest.mock module instead.
