Do not vendor cookbooks using Berkshelf anymore

Instead, use the Berkshelf support in knife-solo and the
vagrant-berkshelf plugin on Vagrant

cookbooks/apt/files/15update-stamp

@@ -1 +0,0 @@
-APT::Update::Post-Invoke-Success {"touch /var/lib/apt/periodic/update-success-stamp 2>/dev/null || true";};