PID File Cleanup

Hi,

It seems that, if the container dies unexpectedly (e.g. power loss), it will not restart properly.

The root cause seems to be some PID files left in /opt/graphite/storage/, specifically carbon-cache-a.pid.

It seems that the PID checker code is not robust enough to know that the process died, so it refuses to start it up again.

Since we're running in a Docker container, perhaps an earlier part of the /etc/my_init.d/01_conf_init.sh file could remove those PID files?

For people using volume mounts on the storage directory this further complicates things. It can prevent carbon-cache from starting up on a newly launched container because the PID files from previously launches remain.