MiqWidgetSet - update seeding lookup
MiqWidgetSet - update seeding lookup

the seeded widget sets set `owner_id` to be a group from the yaml,
then `keep_group_when_saving` sets `group_id` to be the same

so, when looking up the same widget set, `sync_from_file` wouldn't find it by `group_id = nil`.
But we can use `read_only` instead, to limit this to seeded widget sets.

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