Avoid restart when inserting/ejecting adopted.

When rapidly inserting/ejecting an adopted storage device, we might
still be trying to prepare the storage device.  Catch the exception
to avoid a runtime restart, and keep rolling forward, since we'll
probably be handling the ejected event in a few moments to clean up
any packages.

Bug: 28467146
Change-Id: Ib923663ae6d63259c1b5792b68dfe760612ab838