zebra: maintain the router-id per VRF

A router may need different identifier among the VRFs. So move the
maintenance of router-id per VRF.

* rib.h:

  Move the previous global variables in router-id.c into the
  "struct zebra_vrf":
  - struct list _rid_all_sorted_list/*rid_all_sorted_list
  - struct list _rid_lo_sorted_list/*rid_lo_sorted_list
  - struct prefix rid_user_assigned

* router-id.c/router-id.h:

  A new parameter "vrf_id" is added to all the router-id APIs.
  Their operations are done only within the specified VRF.

  A new command "router-id A.B.C.D vrf N" is added to allow
  manual router-id for any VRF.

  The old router_id_init() function is splitted into two:
  - router_id_cmd_init(): it only installs the commands
  - router_id_init(): this new one initializes the variables for
                      a specified VRF

* zebra_rib.c: Add new functions zebra_vrf_get/lookup() called
               from router-id.c.

* main.c: Replace router_id_init() with router_id_cmd_init() and
          call the new router_id_init() in zebra_vrf_new().

Signed-off-by: Feng Lu <lu.feng@6wind.com>
Reviewed-by: Alain Ritoux <alain.ritoux@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: Vincent JARDIN <vincent.jardin@6wind.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/zebra/zserv.c b/zebra/zserv.c
index 85f448c..e17bb72 100644
--- a/zebra/zserv.c
+++ b/zebra/zserv.c
@@ -735,7 +735,8 @@
 
 /* Router-id is updated. Send ZEBRA_ROUTER_ID_ADD to client. */
 int
-zsend_router_id_update (struct zserv *client, struct prefix *p)
+zsend_router_id_update (struct zserv *client, struct prefix *p,
+    vrf_id_t vrf_id)
 {
   struct stream *s;
   int blen;
@@ -1181,9 +1182,9 @@
   /* Router-id information is needed. */
   client->ridinfo = 1;
 
-  router_id_get (&p);
+  router_id_get (&p, VRF_DEFAULT);
 
-  return zsend_router_id_update (client,&p);
+  return zsend_router_id_update (client, &p, VRF_DEFAULT);
 }
 
 /* Unregister zebra server router-id information. */