[PATCH] 9p: fix fid behavior on failed remove

Based on a bug report from Russ Ross <russruss@gmail.com>

According to the spec:

"The remove request asks the file server both to remove the file
 represented by fid and to clunk the fid, even if the remove fails."

but the Linux client seems to expect the fid to be valid after a failed
remove attempt.  Specifically, I'm getting this behavior when attempting to
remove a non-empty directory.

Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>