Add rubocop lint checks

Executed by default rake task.
Remove StubFogInterface

This isn't used by this project. It's a hangover from when this project used
to live in the same repo as the other tools.
Remove unused args from blocks

To fix lint warnings about unused arguments.
Use eq() instead of == in spec tests

To fix lint warning `Operator == used in void context`.
Remove unused var assignment in NetLaunch

To fix lint warning:
```
lib/vcloud/net_launcher/net_launch.rb:22:13: W: Useless assignment to variable - net.
            net = Vcloud::Core::OrgVdcNetwork.provision(net_config)
            ^^^
```
Use be(true) instead of eq(true) in tests

I'm not sure there's strictly a difference. But since there's a specific
matcher for this we might as well use it and differentiate from the string
comparisons.
Change hash indentation in unit tests

To satisfy rubocop's complaints about:

    spec/vcloud/net_launcher/net_launch_spec.rb:12:8: W: end at 12, 7 is not aligned with let!(:network1)
    {{ at 5, 4
          }}
           ^

I don't strictly agree. But hey.
Merge pull request #18 from alphagov/70748484-rubocop_lint

[Fixes #70748484] Rubocop lint checks