package/skeleton-init-systemd: work around for /var/lib not populating

package/skeleton-init-systemd: work around for /var/lib not populating

When using a RO root with systemd, it is intended that /var/lib should be
populated at boot time by tmpfiles system mirroring it from
/usr/share/factory/var/lib.

However, this will only happen if /var/lib does not already exist at the
time systemd-tmpfiles runs.  If it does exist, then tmpfiles will
(silently) skip it and do nothing.

It turns out /var/lib will exist, because some part of systemd creates
/var/lib/systemd/catalog on boot before tmpfiles runs.

The fix used here is to also create tmpfiles entries for the contents of
/var/lib/* and /var/lib/systemd/*.  This way, when those directories
already exist, the entire tree is not skipped and instead the
not-yet-existing contents of /var/lib and /var/lib/systemd will be still
be mirrored from the factory dir.

And if /var/lib/systemd, or a prefix of that, stops getting created and
does not exist, it'll still mirror properly.

It does cause some warnings from systemd:
systemd[1]: Starting Create Volatile Files and Directories...
systemd-tmpfiles[148]: [/etc/tmpfiles.d/var-factory.conf:7] Duplicate line for path "/var/lib/systemd", ignoring.
systemd-tmpfiles[148]: [/etc/tmpfiles.d/var-factory.conf:8] Duplicate line for path "/var/lib/systemd/coredump", ignoring.

But they can be ignored.

IMHO, I think a better solution would be for systemd-tmpfiles to gain a
"merge tree" operation that is like "C" but doesn't abort if the
destination exists, but rather merges the source into it.

Signed-off-by: Trent Piepho <tpiepho@impinj.com>
[yann.morin.1998@free.fr: slight rework of commit title]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Tested-by: Adam Duskett <aduskett@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>