WFCORE-194 Improve Debian/Ubuntu init.d shutdown process

The init.d script for Debian/Ubuntu can be improved in the way it shutdown the server...

If some process hang up, the actual script don't handle that scenario.

This essentially gets all the pids that depends on the process controller, instance servers.

Then sends a TERM signal (clean shutdown) to the pid of the PC, and wait until it finish, if for some reason it doesn't respond and timeout the SHUTDOWN_WAIT then it sends a KILL to force the stop.

Then it checks for any insurgent child process that simply detaches from the PC and kills it.