Resolve faulty use of job control in start script

Job control is not available in shell scripting - only for interactive
sessions, so this strategy of getting the process PID will not work.
Fortunately it is unnecessary - the main process is started by "exec"
which *replaces* the shell process with the new command. Therefore the
script can record it's own PID, and be confident that the java command
that replaces it will take the same PID.