package/samba: use FHS dirs

Clean up system directories by making samba conform to FHS and by using
subdirectories e.g. /var/log/samba and /var/run/samba instead of
/var/log and /var/run.

Signed-off-by: Maxim Mikityanskiy <maxtram95@gmail.com>
Reviewed-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>