its going to get replaced at some point by a busy state. The swap
scripts properly set the next state before unlocking the experiments
table, which possibly leaves some small races as experiments
transition through states (which happens with the table unlocked,
cause I used to have this really handy variable called expt_locked,
which no one really likes anymore).

We either have to use more table locking, fix up expt_locked, or punt
and say it won't happen more than once in a few thousand operations!