Fix failing spec for `bundle plugin list`
Fix failing spec for `bundle plugin list`

Bundler::Plugin::Index#installed_plugins is keys of Hash,
and Hash is not ordered in prior to Ruby 1.9.
So, foo and bar plugins are not always listed in that order.

mvz/bundler,mvz/bundler,bundler/bundler,bundler/bundler,dilumnavanjana/bundler,dilumnavanjana/bundler