OSHMEM: sshmem mmap: use MAP_PRIVATE instead of MAP_SHARED

It looks like using MAP_PRIVATE instead of MAP_SHARED greatly
speeds up infiniband memory registration.

Change-Id: Id7089f58458ef8fff4034a2c4707d31f7e8b6694

oshmem/mca/sshmem/mmap/sshmem_mmap_module.c

@@ -185,7 +185,7 @@ segment_create(map_segment_t *ds_buf,
     addr = mmap((void *)mca_sshmem_base_start_address,
                 size,
                 PROT_READ | PROT_WRITE,
-                MAP_SHARED |
+                MAP_PRIVATE |
 #if defined(MAP_ANONYMOUS)
                 MAP_ANONYMOUS |
 #endif