Improve support for RHEL derivatives

Using $osfamily instead of $operatingsystem to support (more)
derivatives. Unfortunately, $osfamily includes not only RHEL
derivatives but also Fedora. Therefore, further differentiation
by $operatingsystem will still be necessary sometimes.

Change-Id: I61106d9a68ae0dd5689e44d0ab860d445a44633b
Merge "Improve support for RHEL derivatives"