Issue reported by ars3niy: a hasted shopkeeper always gets 2 moves
per turn and had a tendency to move away from the door and then move
right back, keeping it blocked.
I didn't view the ttyrec and didn't reproduce the situation, but I
have noticed something of the sort in the past. This reduces shk
speed so that there will usually be 2 moves per turn but not always,
increasing the likelihood of leaving the door unblocked when nearby
hero does not owe anything.
This change results in a slowed shopkeeper having speed dropped to 11
rather than 12. I suspect that the original 18 speed might have been
picked to guarantee slowed speed of at least 12, but if so, that was
in the days when speed 11 would have provided 11 consecutive moves
and then a turn guaranteed to not allow a move rather than the current
11 out of 12 chance to move each turn.
Fixes#1267
214e508890