do not incrementing/decrementing the opal_progress_event_state.

Per Ralph :
"I noticed that we are incrementing and decrementing the opal_progress_event state.
However, this no longer has any impact whatsoever on the RML as that is running in
the independent ORTE event thread. So all this actually does is impact the MPI layer
by adding an unnecessary overhead."

Thanks Ralph for pointing this :-)

cmr=v1.8.2:reviewer=rhc:ticket=4671