MINOR: connections: Make the "list" element a struct mt_list instead of list.

Make the "list" element a struct mt_list, and explicitely use
list_from_mt_list to get a struct list * where it is used as such, so that
mt_list_for_each_entry will be usable with it.
diff --git a/include/proto/connection.h b/include/proto/connection.h
index 2118d23..65c99a1 100644
--- a/include/proto/connection.h
+++ b/include/proto/connection.h
@@ -318,7 +318,7 @@
 	conn->target = NULL;
 	conn->destroy_cb = NULL;
 	conn->proxy_netns = NULL;
-	LIST_INIT(&conn->list);
+	MT_LIST_INIT(&conn->list);
 	LIST_INIT(&conn->session_list);
 	conn->subs = NULL;
 	conn->idle_time = 0;
diff --git a/include/proto/server.h b/include/proto/server.h
index 06f553e..ca794ab 100644
--- a/include/proto/server.h
+++ b/include/proto/server.h
@@ -261,7 +261,7 @@
 			_HA_ATOMIC_SUB(&srv->curr_idle_conns, 1);
 			return 0;
 		}
-		LIST_DEL_INIT(&conn->list);
+		MT_LIST_DEL(&conn->list);
 		MT_LIST_ADDQ(is_safe ? &srv->safe_conns[tid] : &srv->idle_conns[tid],
 		             (struct mt_list *)&conn->list);
 		srv->curr_idle_thr[tid]++;