server: list number of worker about to be spawned

I am too lazy to count the worker(###) loading... lines so make the
server dump the number of workers it is about to spawn.

Change-Id: I3045e8b7a3ac7de270eb856d8fb6c04e1e6f6e86
server: make master and worker exit(0)

For some reason the master and workers process are exiting with error
code 1.  Seems to me that is the normal behavior and thus it deserves an
exit code of 0.

That would let us kill the server and keep proceeding in Jenkins (which
is usually set to abort whenever a command exit code is not 0).

Change-Id: I25177f911ed54a488579958d0a6236ef36aa2597