Add simple locking between the pool daemon and the mapper so
that the pool daemon does not run while the mapper is working. This will only affect experiments that are using shared nodes though, since the lock is way too coarse and basically serializes the mapper. Since very experiments use hared nodes at this time, it will not really be a problem. Also added TERM handling to avoid killing the daemon while its working, as when stopping testbed daemons to update the installation.