cifs: after upcalling for krb5 creds, invalidate key rather than revoking it

Calling key_revoke here isn't ideal as further requests for the key will
end up returning -EKEYREVOKED until it gets purged from the cache. What we
really intend here is to force a new upcall on the next request_key.

Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/sess.c

@@ -938,7 +938,7 @@ ssetup_ntlmssp_authenticate:
 
 ssetup_exit:
 	if (spnego_key) {
-		key_revoke(spnego_key);
+		key_invalidate(spnego_key);
 		key_put(spnego_key);
 	}
 	kfree(str_area);