pkg/cli/addons/instant: Fix a race condition.
pkg/cli/addons/instant: Fix a race condition.

The w.update call was after app.MutateState, so it could potentially race with a
w.Render call (which calls w.update). Moving it before app.MutateState fixes the
race condition.

This addresses #73.

elves/elvish,elves/elvish,elves/elvish,elves/elvish,elves/elvish