engine : remove unused update states/status

We have some aws-isms in the update code related to different
update states, which is not actually used anywhere, so may as
well remove it - it's probably easier at least for now to focus
on the three update states of COMPLETE/FAILED/REPLACEMENT

Change-Id: Ieeaf92ab0fec6bbfab3dddf2d8fecb0b38c1b2fc
Merge "engine : remove unused update states/status"