Use /run/user/UID in rootless mode if writable
Use /run/user/UID in rootless mode if writable

Other parts of the code are using this directory, so we end up
with us creating an empty directory.

I don't see a reason why we would just use this directory only if
the init program is systemd?

Fixes: https://github.com/containers/podman/issues/10782

Signed-off-by: Daniel J Walsh <7800de746fd39599bc46177380ea6aede7e31e16@redhat.com>

rhatdan/storage,containers/storage,containers/storage,rhatdan/storage,containers/storage,rhatdan/storage