svc: Make svc_sock_release svc_xprt_release

The svc_sock_release function only touches transport independent fields.
Change the function to manipulate svc_xprt directly instead of the transport
dependent svc_sock structure.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
Acked-by: Neil Brown <neilb@suse.de>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Greg Banks <gnb@sgi.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>