osc_base_obj_convert: remove unnecessary MEMCHECKER line

Commit open-mpi/ompi@1a3597aam changed the type of the `convertor`
variable from `ompi_osc_base_convertor_t` (which contained an
`opal_convertor_t`) to an `opal_convertor_t`.  Hence, using memchecker
to ensure that the inner convertor of the `ompi_osc_base_convertor_t`
is considered initialized is now unnecessary.

ompi/mca/osc/base/osc_base_obj_convert.c

@@ -13,6 +13,7 @@
  * Copyright (c) 2009      Sun Microsystems, Inc. All rights reserved.
  * Copyright (c) 2015      Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
+ * Copyright (c) 2015 Cisco Systems, Inc.  All rights reserved.
  * $COPYRIGHT$
  * 
  * Additional copyrights may follow
@@ -109,11 +110,6 @@ int ompi_osc_base_process_op (void *outbuf, void *inbuf, size_t inbuflen,
         opal_convertor_copy_and_prepare_for_recv(ompi_mpi_local_convertor, &datatype->super,
                                                  count, outbuf, 0, &convertor);
 
-        MEMCHECKER(
-            memchecker_convertor_call(&opal_memchecker_base_mem_defined,
-                                      &convertor.convertor);
-        );
-
         do {
             iov_count = OMPI_OSC_BASE_DECODE_MAX;
             done = opal_convertor_raw (&convertor, iov, &iov_count, &size);