SUNRPC: Move upcall out of auth->au_ops->crcreate()

This fixes a bug whereby if two processes try to look up the same auth_gss
 credential, they may end up creating two creds, and triggering two upcalls
 because the upcall is performed before the credential is added to the
 credcache.

 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

include/linux/sunrpc/auth.h

@@ -110,6 +110,7 @@ struct rpc_authops {
 
 struct rpc_credops {
 	const char *		cr_name;	/* Name of the auth flavour */
+	int			(*cr_init)(struct rpc_auth *, struct rpc_cred *);
 	void			(*crdestroy)(struct rpc_cred *);
 
 	int			(*crmatch)(struct auth_cred *, struct rpc_cred *, int);