to document where we are expecting to be called with a lock held to
more easily catch unnoticed code paths.
This does not neccessarily improve locking in pfsync, it just tries
to avoid the panics reported.
PR: kern/159390, kern/158873
Submitted by: pluknet (at least something that partly resembles
my patch ignoring other cleanup, which I only saw
too late on the 2nd PR)
MFC After: 3 days
e999988442