A change in UpdateAutoScalingGroup:
* if a value for MinSize is specified without specifying a value for
DesiredCapacity, and the new MinSize is larger than the current size of
the group, set the group's DesiredCapacity to the new MinSize value
* if a value for MaxSize is specified without specifying a value for
DesiredCapacity, and the new MaxSize is smaller than the current size of
the group, set the group's DesiredCapacity to the new MaxSize value