More build script updates for CI hardware based builds

Fix typo in Vagrantfile memory and CPU handling
Update chefit to create .wgetrc on each VM
Update cluster-assign-roles to error if any command errors, exit 1 on errors, echo password into knife for sudo
Add opscode repo to Ubuntu preseed, do initial disk zapping to ensure hardware boots off the correct disk (due to http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=666974)
Remove opscode repo install from install-chef.sh
Parameterize IP and environment in vbox_create::install_cluster
Update zap-ceph-disks.sh to zap all disks on the system which are not mounted