The fence logic in MPI_Init got messed up somehow such that we were
always executing a fence, which is not desirable. The logic is supposed
to be:
* if async fence is requested and we are not collecting data, then do
not fence at all
* if async fence is requested and we are collecting data, then execute
the fence in the background - wait for completion at the end of MPI_Init.
* if async fence is not requested, then execute a blocking fence at that
point, collecting data as directed. Note that we cannot actually do a
blocking fence as we need to cycle the event library via opal_progress
as the PMIx progress thread is tied to the OMPI event base.
Signed-off-by: Ralph Castain <rhc@pmix.org>