Clean up any stale UNIX domain socket on start

[citrus-it]

If the UNIX socket already exists in the filesystem when fastcgi is started, it fails with

[ Apr 17 12:41:53 Executing start method ("/opt/ooce/sbin/fcgiwrap -s unix:/var/opt/ooce/fcgiwrap/run/fcgiwrap.sock -c 1"). ]
Failed to bind: Address already in use

This patch will automatically clean up any stale socket after checking that nothing is listening on it.