...to avoid missing migrations on Windows and Mac OS X, where existing "3" user
profiles got the "MIGRATED" flag file erroneously added when running LO 3
already, presumably due to 6b522673 "default
config location has changed, look in old config dir when migrating."

(cherry picked from commit 67d23e3a)
Conflicts:
	desktop/source/migration/migration.cxx

Change-Id: I8dd50a36450c167d47411834cc06a754affadf6d
Reviewed-on: https://gerrit.libreoffice.org/1867Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>