Reconsider WIND-DOWN

[ecpeterson]

The anatevka dryad "winds down" at close, to allow blossoms to wrap up whatever stale queries they're performing. (If it closes immediately, then an ongoing stale SCAN e.g. might cause an RTS on a blossom, which causes a crash.) It might be better to make the blossoms responsive to RTSes (e.g., by removing themselves from the computation) than to install this arbitrary delay.