Fix GUIAction::operation_start

We need to set the value of tw_operation_state a little sooner to
make the decrypt page work correctly. Without this change, decrypt
would incorrectly display the main page during the first decrypt
cycle. This fix may also fix ORS and possibly other things that
use the runPage function.

Change-Id: I85ad6e4add6726a2746eeb7116f3eab3f7ff5d84