reset receive request convertor for persistent requests

We can always call unpack.. 

This commit was SVN r10677.

ompi/mca/mtl/base/mtl_base_datatype.c

@@ -98,10 +98,10 @@ ompi_mtl_datatype_unpack(struct ompi_convertor_t *convertor,
     max_data = iov.iov_len;
 
     
+    ompi_convertor_unpack(convertor, &iov, &iov_count,
+                          &max_data, &free_after);
 
     if (max_data > 0 && ompi_convertor_need_buffers(convertor)) {
-        ompi_convertor_unpack(convertor, &iov, &iov_count,
-                          &max_data, &free_after);
         free(buffer);
     }
 

ompi/mca/pml/cm/pml_cm_recvreq.h

@@ -137,6 +137,11 @@ do {                                                                    \
         MCA_PML_CM_RECV_REQUEST_RETURN( recvreq );                      \
     } else {                                                            \
         /* initialize request status */                                 \
+        if(recvreq->req_recv.req_base.req_ompi.req_persistent) {        \
+            /* rewind convertor */                                      \
+            size_t offset = 0;                                          \
+            ompi_convertor_set_position(&recvreq->req_recv.req_convertor, &offset); \
+        }                                                               \
         recvreq->req_recv.req_base.req_pml_complete = true;             \
         MCA_PML_CM_RECV_REQUEST_MPI_COMPLETE( recvreq );                \
     }                                                                   \