rma: fix semantic errors in osc/rdma and MPI_Win_fence

 - Return an error if the caller specified both MPI_MODE_NOPRECEDE and
   MPI_MODE_NOSUCCEED to MPI_Win_fence.

 - Return an error if the caller attempts to enter an active target
   epoch while already in a passive target epoch.

 - End an active target epoch if MPI_Win_fence is called with
   MPI_MODE_NOSUCCEED.

cmr=v1.7.5:ticket=#4382
osc/rdma: do not use MPI_SOURCE to determine the peer in an send operation.

This fixes a bug in r31029 which removes the use of the pml base request
(also not a good way since cm doesn't use the base request). We now allocate
a data structure (ugh) to determine the needed information. Tested with
mtt/onesided.

cmr=v1.7.5:ticket=#4379