Previously the release package was chosen by picking the first package
that provides 'system-release' that isn't named generic. This can cause
branding issues with repos containing multiple system-release packages.
This patch changes _install_branding so that it will give preference to
a system-release package that ends with lowercase --variant name. If
there isn't one it will fall back to the previous behavior.
Resolves: rhbz#1826479
3613c12464