pendingPromise in form-autocomplete is inside out

In the blur event for form-autocomplete we create a pendingPromise to ensure that behat does not move on to a next step.
However we are then adding .then conditions to that promise.

Unfortunately that means that we complete the M.util.js_complete before we actually select the item or close the list.

It's not a major bug, but it could theoretically cause some random failures and we should fix it.