Remove net lock from DIOCGETTIMEOUT

Remove net lock from DIOCGETTIMEOUT

'pfctl -s timeouts' values are only used inside of pf, entirely protected
by the pf lock through the ioctl interface;  the net lock is useless.

Previous attempts to remove net lock usage showed that the pf lock cannot
yet entirely replace it, so start with small pieces like this one.

Contrary to IPv4/6 read-only ioctls, some pf ioctls without FWRITE flag do
modify internal pf state, which is not entirely obvious when approached
from the ioctl layer.

OK sashan dlg