api: refactor api data storage

single struct to hold all api handler, flags, etc.
Provide functions to toggle flags instead of writing directly to
internal data.

Type: refactor
Change-Id: I4730d7290e57489de8eda34a72211527e015b721
Signed-off-by: Damjan Marion <damarion@cisco.com>

src/vlibmemory/vlib_api.c

@@ -340,7 +340,7 @@ vlib_apis_hookup (vlib_main_t *vm)
    */
   msg_id_base = setup_message_id_table ();
 
-  am->is_mp_safe[VL_API_GET_NODE_GRAPH] = 1;
+  vl_api_set_msg_thread_safe (am, VL_API_GET_NODE_GRAPH, 1);
   return 0;
 }