Reorder migration of settings from db to xml

Make sure we commit the Global table last, so that if the
runtime was restarted before the others were written, we don't
get into an inconsistent state of migration.

Not sure if this fixes the following bug, but it's one thing
that stood out as a possibility.

Bug: 27335488
Change-Id: I4166a157e9ff542b1d5e32797693417375e40581