vnf-update don't change heat stack's state.
But update_wait function currently check stack's state.
Therefore update_wait always raise exception,when tacker
execute update. The reason that this function execute
check process is because vdu_autoheal action shares
update_wait with update action.
this commit splits update_wait into heal_wait and update_wait.
Closes-Bug:#1837205
Change-Id: I7ab059bb30b5de38943555883a92d77a64a56d34