Fix integration test for MPI time accounting.
Fix integration test for MPI time accounting.

- Region time is accounted for differently than MPI time.
- MPI time is accumulated if any rank is in an MPI call, but
  region time is accumulated when all ranks are in a region.
- For this reason comparison of MPI time and region time
  requires an error that is perportional to the time not
  attibuted to regions.

Change-Id: I41c163a29b157ece0f29932752fc1c43d71f5b98
Signed-off-by: Christopher M. Cantalupo <9cf3ecca60a3dd7112ab0e7250bedb8a752e3958@intel.com>

geopm/geopm,cmcantalupo/geopm,geopm/geopm,cmcantalupo/geopm,cmcantalupo/geopm,cmcantalupo/geopm,geopm/geopm,geopm/geopm,cmcantalupo/geopm,geopm/geopm