r1117: Doh ! Remember to turn off signing when sending a "break to level II" oplock

r1117: Doh ! Remember to turn off signing when sending a "break to level II" oplock
message, or we mess up the signing sequence number.... Also improve sign error
reporting. Also when deferring an open that had been deferred due to an oplock
break, don't re-add the mid to the pending sign queue or we increment the sequence
number twice and mess up signing again...
I can now bounce between 2 WinXP/Win2003 boxes opening Excel spreadsheets with
signing turned on and get correct "file in use" messages.
Jeremy.
(This used to be commit 1745ce4e2cf7fcb4c27c077973258d157cd241b1)