sunrpc: Use userns friendly constants.

Instead of (uid_t)0 use GLOBAL_ROOT_UID.
Instead of (gid_t)0 use GLOBAL_ROOT_GID.
Instead of (uid_t)-1 use INVALID_UID
Instead of (gid_t)-1 use INVALID_GID.
Instead of NOGROUP use INVALID_GID.

Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

net/sunrpc/auth.c

@@ -519,8 +519,8 @@ rpcauth_bind_root_cred(struct rpc_task *task, int lookupflags)
 {
 	struct rpc_auth *auth = task->tk_client->cl_auth;
 	struct auth_cred acred = {
-		.uid = 0,
-		.gid = 0,
+		.uid = GLOBAL_ROOT_UID,
+		.gid = GLOBAL_ROOT_GID,
 	};
 
 	dprintk("RPC: %5u looking up %s cred\n",