Fixed: Upgrading stale packages before git installation (git might be even missing if packages are too old)

Fixed: Upgrading stale packages before git installation (git might be even missing if packages are too old).
I didn't verified this code on CentOS as I don't have any CentOS-based box running. But without this line for Debian I was unable to install GIT on Debian using the following box: `http://andrew.mcnaughty.com/downloads/squeeze64_puppet27.box`