Lock mutex in call to runStatus()

Lock the mutex near the top of the runStatus function.  Until recently,
this wasn't necessary, but #9397 made it possible for the background
thread to change m_status and m_deferredRunDetailsPkt while runStatus is
executing in the foreground.

Refs #9748
Minor comment & log updates

Fixed a few comments and also changed a few log statements from debug
level to warning level.

Refs #9748
Merge remote branch 'origin/bugfix/9748_live_listener_race'