api: revert the changes to atexit for shared memory client

2ca88ff978 introduced the change
into the shared memory atexit, which breaks IPSec tests in some
environments.

Type: fix
Fixes: 2ca88ff978
Change-Id: Ia132cb045e8d66f55e41d29cffdca3458d61096d
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>

src/vlibmemory/memory_api.c

@@ -1029,7 +1029,7 @@ vl_api_client_index_to_input_queue (u32 index)
 static clib_error_t *
 setup_memclnt_exit (vlib_main_t * vm)
 {
-  atexit (vl_unmap_shmem_client);
+  atexit (vl_unmap_shmem);
   return 0;
 }