probe the actors when there is inactivity

argonnite-2014-07-10-2.pbs
mppwidth=384
walltime=00:03:40
node 15 efficiency: 0.30

argonnite-2014-07-10-16-1.pbs
mppwidth=384
walltime=00:05:45
node 5 efficiency: 0.20

argonnite-2014-07-10-64-4.pbs
mppwidth=1536

argonnite-2014-07-10-16-2.pbs
mppwidth=384
walltime=00:03:31
node 1 efficiency: 0.31

https://github.com/GeneAssembly/biosal/issues/389
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>