Replace backtick command substitutions with $(), quote variable
expansions to prevent word splitting, replace useless cat pipes with
redirections, use grep -q instead of redirecting to /dev/null, and use
bash parameter expansion for case conversion.
Based on the work from PR #6366, rebased and adapted to current master.
Shebangs already merged separately via df64bf8fe are excluded.
Co-Authored-By: Samveen <samveen@yahoo.com>
RH7/Centos7 and recent versions of fedora relocate `/*bin/*` into `/usr/*bin/`. This causes
conflicts for upgrades against xCAT-genesis-scripts-* packages which expect the `/bin` a to be
a directory while `xCAT-genesis-base-*` packages provide a link. Relocating all files into `/usr`
fixes that conflict and allows a clean upgrade from all old versions.