Fix ruby-191-prep to install bundler

Still trying to get ruby 1.9.x as default for gate jobs on precise.
* install the bundler gem under 1.9.x
* make sure do to update before trying to install libgecode-dev

Change-Id: I61df9fd3a94670bb10bac8bb4d820a66f25d7675
Closes-Bug: #1357439
Merge "Fix ruby-191-prep to install bundler"