PID lock file doesn't work well when running Horcrux inside Docker

[lhopki01]

When Horcrux is run inside Docker the PID it is assigned is almost always the same one. If Horcrux shutsdown improperly and leaves behind the PID lock file then there are issues. The current check panics if the current PID is the same as the PID in the file and doesn't clean up the file like it does if the PIDs are different and the lock file PID doesn't exist anymore.

horcrux/signer/services.go

Lines 37 to 40 in a15c3d6

	if int(pid) == os.Getpid() {
	panic(fmt.Errorf("error checking PID file: %s, PID: %d matches current process",
	pidFilePath, pid))
	}

Could this check be removed or a flag added to ignore it?

[lhopki01]

Currently we have to do this on every start.

if [ -f /home/horcrux/.horcrux/horcrux.pid ]; then
  echo "Fixing PID lock file till https://github.com/strangelove-ventures/horcrux/issues/250 is addressed"
  echo 9999 > /home/horcrux/.horcrux/horcrux.pid
fi