Fix potential hangs for fast-fail jobs

When a job fails very quickly, it is possible that the spawning tool
won't get notified that the spawn completed prior to be told that the
job terminated. This can cause the tool to "hang" in PMIx_Spawn. Ensure
that PRRTE handles this case by guaranteeing we notify the spawner.

Track both PRRTE and PMIx masters as both have changed, though only the
PRRTE one is involved in this particular fix.

Signed-off-by: Ralph Castain <[email protected]>

Author: rhc54