To avoid unprivileged users being able to interfere with the creation of the
private snap mount namespace, instead of creating this as /tmp/snap.$SNAP_NAME/
we can now use the systemd-tmpfiles configuration to do this for us
at boot with a known fixed name (/tmp/snap-private-tmp/) and then use that as
the base dir for creating per-snap private tmp mount
namespaces (eg. /tmp/snap-private-tmp/snap.$SNAP_INSTANCE/tmp) etc.
Signed-off-by: Alex Murray <alex.murray@canonical.com>
21ebc51f00