pml/cm: fix buffer usage in MCA_PML_CM_HVY_SEND_REQUEST_BSEND_ALLOC()

In MCA_PML_CM_HVY_SEND_REQUEST_BSEND_ALLOC(), after call to
opal_convert_pack() will changed convertor's status, the convertor
need to be reset to original state.

This is achieved by calling opal_convertor_prepare_for_send(),
and it should be called with original send buffer provided by
application, which is sendreq->req_addr.

However, prior to this change, the function was called with
sendreq->req_buff, which is the temprary buffer used for send.

As a result, when the same request is used the 2nd time, wrong
data was copied to outgoing buffer, and caused memory corrupiton.

This patch addressed the issue.

Signed-off-by: Wei Zhang <wzam@amazon.com>

Author: wzamazon

ompi/mca/pml/cm/pml_cm_sendreq.h

@@ -381,7 +381,7 @@ do {                                                                    \
                                  &max_data );                           \
             opal_convertor_prepare_for_send( &sendreq->req_send.req_base.req_convertor, \
                                              &(ompi_mpi_packed.dt.super),  \
-                                             max_data, sendreq->req_buff ); \
+                                             max_data, sendreq->req_addr ); \
         }                                                               \
     }                                                                   \
  } while(0);