NFS: Remove duplicate svc_xprt_put from nfs41_callback_up

The xprt created by svc_create_xprt have be added to serv->sv_permsocks.
So putting the xprt directly is useless.
Otherwise, there is a more svc_xprt_put after the xprt be freed.

v2, same as v1.

Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>