SUNRPC: Clean up the RPCSEC_GSS service ticket requests

Instead of hacking specific service names into gss_encode_v1_msg, we should
just allow the caller to specify the service name explicitly.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index 7748d6a..6f3ebb4 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -718,7 +718,7 @@
 {
 	if (callback_cred)
 		return 0;
-	callback_cred = rpc_lookup_machine_cred();
+	callback_cred = rpc_lookup_machine_cred("nfs");
 	if (!callback_cred)
 		return -ENOMEM;
 	return 0;