Update TODO.asciidoc
Don't start upgrade if media can't be mounted (#984415)

If the upgrade media can't be mounted, we probably shouldn't start the
upgrade. Therefore, let's put the upgrade media in '.requires' instead of
'.wants'.
disable deltarpm harder (#1005895)

deltarpm has crept into yum core, so disabling the "presto" plugin
isn't enough anymore. Set "deltarpm=0" in the yum conf to turn it off
for real.