Make inserting existing references work again

When MWReferenceDialog was modified to inherit from ActionDialog the
search select method didn't get changed to call applyChanges. But really,
you can't just call applyChanges because you need all the promise setup
stuff that onApplyButtonClick does. The API for ActionDialog needs to be
improved, but this works just fine in the mean time.

Bug: 64677
Change-Id: Ib38a624811dc26ead7b9de64cb41aff642820452
Merge "Make inserting existing references work again"