Cleanup yum things

We no longer support platforms with Yum on master.  Cleanup old
references and convert to dnf.

We don't need any of the failure wrapper stuff as dnf runs in strict
mode by default.

There seem to be a few callers out there, so we'll leave it called
yum_install for now.

Change-Id: Ie71a48fd85b00a97a14bf260cd013b18af4cce06
3 files changed