SUNRPC: Remove extra xprt_put()

While testing error cases where rpc_new_client() fails, I saw
some oopses.

If rpc_new_client() fails, it already invokes xprt_put().  Thus
__rpc_clone_client() does not need to invoke it again.

Introduced by commit 1b63a751

 "SUNRPC: Refactor rpc_clone_client()"
Fri Sep 14, 2012.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Cc: stable@vger.kernel.org [>=3.7]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>