Fix tests to stub the with https

[thinkerbot]

I'm not sure what the difference is but my hypothesis is that the old set of stubs don't work with old docker versions (I'm on 1.6.1 currently). Could be old docker parses urls in a more naive way and forces the protocol from tcp => https. I was getting errors like:

  "this is stubbed"
  stub_request(:get, "http://tcp//example.com:5422/v1 ...

  "you need to stub this"
  stub_request(:get, "https://example.com:5422/v1 ...

And note this is how the docker url is set in the helper:

  Docker.url = 'tcp://example.com:5422'

Probably should not merge this if this fix doesn't work on newer docker. Might be I should just upgrade.

[joshughes]

This change causes Travis to fail. Docker should not even been installed on the system for the tests to work... we are mocking out each call that should be made I am fairly sure. Also my docker version is 1.9.2. I know for a fact that Travis has no docker installed though... I still think this is some sort of system setting or version problem.