checkpoint on adding rolling update support.

many tests pass, a few don't.

Change-Id: I3ac03561754c988254eab338979930c66d110f03
another checkpoint: fixed one test case

we need to avoid considering more of the old resources than the
number of units we need to have.

Change-Id: Idf1a1d1fc8353945ff01a704600b84b4171364ef
autoscaling code now uses aslib for rolling update

all tests pass!

Change-Id: I8635b335213fe3cf5b22facd4b72bac75b0a7ec9