resgroup: add rolresgroup to pg_roles.

rolresgroup was added to pg_authid in previous commits, we also should
add it to pg_authid.
Signed-off-by: NNing Yu <nyu@pivotal.io>

src/backend/catalog/system_views.sql

@@ -26,7 +26,8 @@ CREATE VIEW pg_roles AS
         rolcreaterexthttp,
         rolcreatewextgpfd,
         rolcreaterexthdfs,
-        rolcreatewexthdfs  
+        rolcreatewexthdfs,
+        rolresgroup
     FROM pg_authid;
 
 CREATE VIEW pg_shadow AS