Better handling of process statuses when stopping a process:
 * After stopping, only processes no longer executing are marked as stopped
 * Processes that didn't immediately stop will keep status STOPPING and handled
   by monitoring

Make cpcd process monitor (repeatably) kill process with SIGKILL if nice
shutdown (SIGTERM) takes longer than 5 seconds.

Made cpcd always remove process definition when undefine process have been
issued for process and process has stopped.

undefine process no longer returns failure when process is still running
at the time, only if process is not defined or undefine is already in progress.

Change contributed and reviewed jointly with Tiago Alves.