OSC base: do not retain datatype by default

Signed-off-by: Joseph Schuchart <schuchart@hlrs.de>
(cherry picked from commit 154cf571b6a6996ff6ba9e0860f5d6a6fcf2d425)

ompi/mca/osc/base/osc_base_obj_convert.h

@@ -54,7 +54,6 @@ ompi_osc_base_datatype_create(ompi_proc_t *remote_proc,  void **payload)
     struct ompi_datatype_t *datatype =
         ompi_datatype_create_from_packed_description(payload, remote_proc);
     if (NULL == datatype) return NULL;
-    OMPI_DATATYPE_RETAIN(datatype);
     return datatype;
 }