Commits on Feb 11, 2015

1. agentctl.sh: Sanity check PID_FILE and remove at stop …

   PID files are inherently problematic because PIDs are reused.  This
   means that at start up if we find a PID file and there is a running
   process with that PID we do nothing.  Unfortunately it is possible that
   our process long since died, PIDs have wrapped and are now getting
   reused and the process we found is an unrelated process.  The problem is
   even more likely at system start time if we find a PID file from the
   previous system boot.  In this case the system is starting up and
   spawning many new processes and it is likely that the low numbered PID
   we received on the previous boot will be near other processes starting
   in parallel.
   
   To help solve this problem we can remove stale PID files when we shut
   down cleanly.  Additionally we can perform a basic sanity check if we
   find a PID file and find the PID running to compare that they at least
   have the command we expect.  This commit performs both of these actions.
   
   Additionally PID files are typically written to /var/run or /run
   which get cleared on reboots.  I am not making that change since I do
   not know if there would be any ramifications to moving the location of
   the PID file.
   
   Signed-off-by: Shawn Bohrer <[email protected]>

   Shawn Bohrer committed Feb 11, 2015
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