sock api: add infra for bootstrapping shm clients

- add function to sock client that bootstraps shm api
- allow sock clients to request custom shm ring configs

Change-Id: Iabc1dd4f0dc8bbf8ba24de37f4966339fcf86107
Signed-off-by: Florin Coras <fcoras@cisco.com>
diff --git a/src/vat/vat.h b/src/vat/vat.h
index 1ae46f3..ddb4644 100644
--- a/src/vat/vat.h
+++ b/src/vat/vat.h
@@ -209,7 +209,7 @@
   ip4_nbr_counter_t **ip4_nbr_counters;
   ip6_nbr_counter_t **ip6_nbr_counters;
 
-  socket_client_main_t socket_client_main;
+  socket_client_main_t *socket_client_main;
   u8 *socket_name;
 
   /* Convenience */