svc_xprt_put() can call tcp_close(), which can sleep, so we shouldn't be
holding this lock.

In fact, only the xpt_list removal and the sv_tmpcnt decrement should
need the sv_lock here.
Reported-by: NMi Jinlong <mijinlong@cn.fujitsu.com>
Signed-off-by: NJ. Bruce Fields <bfields@citi.umich.edu>