Fix a bug in appwidget migration to multiuser directory.

Bug: 6393606

Migrate the old appwidgets.xml if the file doesn't exist,
not if the directory doesn't exist. It worked earlier because
this was the first service that I migrated to multi-user :(

Change-Id: I59bcbc31ff9d101e44dff5e5f44b3cab8f08dc06
1 file changed