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>
diff --git a/net/sunrpc/auth_unix.c b/net/sunrpc/auth_unix.c
index 52c5abd..2f86270 100644
--- a/net/sunrpc/auth_unix.c
+++ b/net/sunrpc/auth_unix.c
@@ -85,7 +85,7 @@
 		cred->uc_gids[i] = gid;
 	}
 	if (i < NFS_NGROUPS)
-		cred->uc_gids[i] = NOGROUP;
+		cred->uc_gids[i] = INVALID_GID;
 
 	return &cred->uc_base;
 }
@@ -137,7 +137,7 @@
 			return 0;
 	}
 	if (groups < NFS_NGROUPS &&
-	    cred->uc_gids[groups] != NOGROUP)
+	    cred->uc_gids[groups] != INVALID_GID)
 		return 0;
 	return 1;
 }
@@ -166,7 +166,7 @@
 	*p++ = htonl((u32) cred->uc_uid);
 	*p++ = htonl((u32) cred->uc_gid);
 	hold = p++;
-	for (i = 0; i < 16 && cred->uc_gids[i] != (gid_t) NOGROUP; i++)
+	for (i = 0; i < 16 && cred->uc_gids[i] != INVALID_GID; i++)
 		*p++ = htonl((u32) cred->uc_gids[i]);
 	*hold = htonl(p - hold - 1);		/* gid array length */
 	*base = htonl((p - base - 1) << 2);	/* cred length */