Auto merge of #4018 - philnash:removing_duplication, r=segiddins
Auto merge of #4018 - philnash:removing_duplication, r=segiddins

Removes duplication from bundle clean command

I was not feeling inspired, but I do like to delete code! Here's a small simplification as reported [in Code Climate](https://codeclimate.com/github/bundler/bundler/Bundler::Runtime).

asutoshpalai/bundler,RochesterinNYC/bundler,bronzdoc/bundler,asutoshpalai/bundler,Teino1978-Corp/Teino1978-Corp-bundler,mvz/bundler,suhastech/bundler,zhangkuaiji/bundler,bronzdoc/bundler,zhangkuaiji/bundler,seanlinsley/bundler,jingweno/bundler,davydovanton/bundler,bundler/bundler,dilumnavanjana/bundler,ipmobiletech/bundler,h4ck3rm1k3/bundler,jingweno/bundler,suhastech/bundler,mpapis/bundler,mvz/bundler,simplybusiness/bundler,ipmobiletech/bundler,pivotal-cf-experimental/bundler,joshsoftware/bundler,davydovanton/bundler,mpapis/bundler,dilumnavanjana/bundler,pivotal-cf-experimental/bundler,jasonkarns/bundler,bundler/bundler,jasonkarns/bundler,simplybusiness/bundler,seanlinsley/bundler,RochesterinNYC/bundler,h4ck3rm1k3/bundler,joshsoftware/bundler,Teino1978-Corp/Teino1978-Corp-bundler