Accordion should accommodate changed isOpen props

[mnicole]

If the accordion is locked and props.isOpen initial value changes (not through the actions of a user), then it should update the accordion.

For example, if you want the accordion to be locked to the user's actions, but load some data into it that comes back after the component mounts, and you need to open it when the data gets returned, this is currently not possible.

*Internal note - after this is merged we should update our AM project to use it (see PR for AM-135)