MFC: r199053

MFC: r199053
Add a check for the connection being shut down to the krpc
client just before queuing a request for the connection. The
code already had a check for the connection being shut down
while the request was queued, but not one for the shut down
having been initiated by the server before the request was
in the queue. This fixes some cases of problems w.r.t. reconnecting
to a NFS server that drops inactive TCP connections.

Tested by:	Olaf Seibert, Daniel Braniss
Reviewed by:	dfr

git-svn-id: svn://svn.freebsd.org/base/stable/8@199293 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f