r2413: Arggg. Stupid, stupid, stupid me ! I added a paranoia test

r2413: Arggg. Stupid, stupid, stupid me ! I added a paranoia test
case when I was developing the deferred open case and made it
too tight. It will fire (incorrectly) and panic when a client
does a second open for a file with a different mid (multiplex-id)
request. Doh ! This is a perfectly valid thing for a client to
do (have two pending opens with different mids outstanding on
the same file) and currently when the first pending open expires
with a share violation the paranoia code will panic smbd.

It's a rare condition, but obvious now I've looked at the
code.

Fix for bug #1743.

Jeremy.
(This used to be commit e1bf108ae965ae730c67524164fa36497ea905b5)