Don't lose transaction callbacks that are still in the drawing state.

When a message invalidate occurs, the current state will be copied into
drawing state. If another invalide occurs before a refresh, the new
current state will be copied into the drawing state. That means we
would lose any transaction callbacks that were sent with the first
transaction. When refresh is called, we will not notify the callbacks
from the first transaction and the system will get stuck waiting for
callbacks forever.

Test: No direct steps to reproduce. Open apps a lot with blast and
make sure system doesn't freeze.

Change-Id: I820027e86b15e082e5e7092b2ee52e90a2328d38