svc: Clean up deferred requests on transport destruction

svc: Clean up deferred requests on transport destruction

commit 22945e4a1c7454c97f5d8aee1ef526c83fef3223 upstream.

A race between svc_revisit and svc_delete_xprt can result in
deferred requests holding references on a transport that can never be
recovered because dead transports are not enqueued for subsequent
processing.

Check for XPT_DEAD in revisit to clean up completing deferrals on a dead
transport and sweep a transport's deferred queue to do the same for queued
but unprocessed deferrals.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Cc: roma1390 <roma1390@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>