Ruby client tests fail on Riak 2.0

### TL;DR

The rake gem is installed, but I still get the error

`07:32:46.124 [info] /home/buildbot/.gem/gems/bundler-1.5.0/lib/bundler/spec_set.rb:92:in `block in materialize': Could not find rake-10.1.1 in any of the sources (Bundler::GemNotFound`

/cc @bkerley

### Problem

I compiled ruby 1.9.3 from source to properly run riak_test client_ruby_verify of the testers.  I gem installed all the gems needed for the test when they failed during the test.  Even after install rake, the test still failed.

### Complete Log

http://giddyup.basho.com/#/projects/riak_ee/scorecards/66/66-285-client_ruby_verify-centos-6-64-memory/31098/artifacts/439625