Add support for the openSUSE Leap distributions. Nothing special is
required for this except adding the appropriate distro variables
file and also update the zypper cache before package installation. We
also had to apply the same virtualenv-tools fix similar to CentOS.
Change-Id: I8bbf0af1149e4c5ea39f82e4fa7be78578cf6a50
abafaee5c1