Consistency checks: Distinguish "entry" from exit

Consistency checks: Distinguish "entry" from exit

Many externally-facing functions are called by adns itself.  In such a
case, on entry, there may be intdone queries in flight.  This is fine.

So distinguish cc_enter from cc_exit, and check intdone only on
cc_exit.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>