package/samba4: create tempfile with systemd

With systemd, samba4 will need some special temporary files to be
created on each boot, as explained in:
    packaging/systemd/README

Install the provided template file as configuration.

However, this is not enough, as even the log directory is a tmpfs in
the default Buildroot configuration, so we must also create the log
directory on each boot. Hence we append this to the template installed
above.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Gustavo Zacarias <gustavo@zacarias.com.ar>
Acked-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>