Add an option --cleanup-post to cleanup packages in post scripts.

Resolves: rhbz#1070603
Add a Requires for a sufficiently new yum

Resolves: rhbz#1084165
Disable screen blanking

Resolves: rhbz#1070112
Clear upgrade.conf before starting

This will remove any stale configuration from a previous run of
fedup before starting a new upgrade.

(cherry picked from commit e38b00477b0cd8418624b0008db41fbf4356ad62)

Related: rhbz#1100391
Don't cleanup upgrade.conf for now

Work around a bug in redhat-upgrade-dracut in which the cleanup script
is run before the post-upgrade scripts. The post-upgrade scripts depend
on upgrade.conf, which would normally be removed by the cleanup.

Related: rhbz#1100391
New release 0.7.15
Run realpath on --device arguments.

This way arguments like /dev/cdrom (a symlink), /mnt/ (trailing slash),
or ./../path/../..////../media/../srv/install (madness) will work as
expected.

(cherry picked from commit 25ab8765dbb46c768bc9a706661de36ed0082767)

Resolves: rhbz#1083169
New release 0.7.16