install: Always use bare-user-only repos for child repos
install: Always use bare-user-only repos for child repos

This way everything works with /var/tmp on tmpfs or other non-xattr system
by default. The reason we used to use bare-user for the child repo is that bare-user-only
can't represent all possible ostree repos. For instance a file non-canonical permissions
such as "readable by user but not other/group" cannot be stored. Reading back such a file
when commiting to the real repo would give you a repo-corrupt error.

However, its been a long time since we made flatpak always generate canonical permissions
for all exports, so at this point I think its safe to switch this over by default.

This also fixes https://github.com/flatpak/flatpak/issues/1622

Closes: #1686
Approved by: alexlarsson

matthiasclasen/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,matthiasclasen/flatpak,flatpak/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak