osc/rdma: quiet warning in r31197

cmr=v1.8:ticket=trac:4441

This commit was SVN r31223.

The following SVN revision numbers were found above:
  r31197 --> open-mpi/ompi@0ed44f2fdb

The following Trac tickets were found above:
  Ticket 4441 --> https://svn.open-mpi.org/trac/ompi/ticket/4441

ompi/mca/osc/rdma/osc_rdma_comm.c

@@ -419,7 +419,7 @@ ompi_osc_rdma_accumulate_w_req (void *origin_addr, int origin_count,
     size_t ddt_len, payload_len, frag_len;
     char *ptr;
     const void *packed_ddt;
-    int tag;
+    int tag = -1;
 
     OPAL_OUTPUT_VERBOSE((50, ompi_osc_base_framework.framework_output,
                          "acc: 0x%lx, %d, %s, %d, %d, %d, %s, %s, %s",