Handle abort correctly during installation

bnc#893638
Please avoid `be_true`, it is incompatible with RSpec 3. Use `eql true` like everywhere else.

But in this case, how about
```ruby
expect(NetworkLanComplexInclude)
 .to receive(:ReallyAbort)
 .and_return("placeholder (true or false)")

 expect(NetworkLanComplexInclude.input_done?(:abort)).to eql "placeholder (true or false)"
```