Returning to wizard, enable migration.

Bring primary storage migration back into the adoption flow, and
provide a path for long-lived notifications to re-launch into the
Settings app.  Also provide option to initiate migration if skipped
during wizard.  For now, estmiate migration size and time based on
a Class 10 card.

Follow other callback refactoring.

Bug: 19993667
Change-Id: Ia0c28eb114bc6c8066c17b3142ed74f962140c91