stale pid files for carbon-cache left

[dkiser]

On subsequent runs of the container that has exited, stale pid files are kept in the GRAPHITE_STORAGE_DIR per the code in lib/carbon/conf.py.

Supervisord should have a cleanup method to rm -f GRAPHITE_STORAGE_DIR/*.pid on startup.

PID left in ephemeral docker volume from last run of container:

root@b8b663787929:/var/lib/graphite# ls -la /var/lib/graphite/storage/*.pid
-rw-r--r-- 1 www-data www-data 1 Jan 19 21:49 /var/lib/graphite/storage/carbon-cache-a.pid

Error observed:

root@b8b663787929:/var/lib/graphite# tail /var/log/supervisor/carbon-cache.log
carbon-cache (instance a) is already running with pid 9
carbon-cache (instance a) is already running with pid 9
carbon-cache (instance a) is already running with pid 9
carbon-cache (instance a) is already running with pid 9
carbon-cache (instance a) is already running with pid 9
carbon-cache (instance a) is already running with pid 9
carbon-cache (instance a) is already running with pid 9
carbon-cache (instance a) is already running with pid 9
carbon-cache (instance a) is already running with pid 9
carbon-cache (instance a) is already running with pid 9