Add support for the openSUSE Leap distributions. Nothing special is
required for this except for adding the appropriate distro variables
file and also update the zypper cache before package installation.
Moreover, the syslog user belongs to the 'users' group instead of a
dedicated 'syslog' group so we adjust the defaults for openSUSE.
Depends-On: I96c02fb2ee26691f1d7dd449d7205baa231795fe
Change-Id: I86beac2b3e038a0a4a3bf9618218bc1e393bdf08