heat engine : fail update immediately on resource update failure

When doing an update, we want to fail immediately, instead of
collecting the resource update errors and continuing.  This is
particularly important for update rollback, where we want to
declare failure ASAP to simplify and speed up the rollback

blueprint update-rollback

Change-Id: I56133254036d8aac592dcf3cda2ca7928cc02fa9
heat engine : Update stack dependencies during update

We need to update the stack dependencies each time we modify the
resources list, otherwise in the event of a failure, the resources
returned from the iterator methods don't match with those found via
getitem/contains (which is important for rollback)

blueprint update-rollback

Change-Id: Ia47f84291f50c33fc052b7b33fa0c1f9e8430ab4
Merge "heat engine : fail update immediately on resource update failure"
Merge "heat engine : Update stack dependencies during update"