Added the ability to aptpkg.upgrade to use the upgrade opition with apt-get instead of the dist-upgrade method.  Introducing a new argument to the upgrade function, dist-upgrade, which is True by default but can be set to False to use upgrade.
lint issues
Merge pull request #13327 from garethgreenaway/11859_add_flag_to_aptpkg_for_upgrade

Added the ability to aptpkg.upgrade to use the apt-get upgrade opition instead of dist-upgrade