pkg.list_upgrades: Ignore "downloading" lines in pacman output
pkg.list_upgrades: Ignore "downloading" lines in pacman output

It appears that Antergos distributes a modified version of pacman which
adds additional lines while updating its package databases. These are
incorrectly interpreted as available upgrades. This commit checks for
these lines in the output and skips them.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt