The Fedora .repo files no longer use mirrorlist= for metalink.

Simplify Repo._try_revive() a bit. Also awaiting a change in librepo to use
LRO_METALINK.

Related: RhBug:948788
remove: dnf.yum.config.mirrorlist_expire, it's unused.
remove: couple of config options (kernelpkgnames, exactarch, rpm_check_debug).

Unused.
logging: do not show 'Downloading packages:' on remove. (RhBug:1008444)
New version: 0.4.1
build: 0.4.1-1