Check if build is cancellable in client

Bugzilla - https://bugzilla.redhat.com/show_bug.cgi?id=1171673
> End to end is a test that tests our integration "end to end". 

I know, was I was trying to say is that I'm trying to run a simple command and assert it works, `test-cmd.sh` should be the proper place, as you said.

> if you want to test it there it should be start-build -> cancel build immediately.
I do just that, the thing is sometimes the build completes very fast and the command exists because you can't cancel a complete/failed build. To avoid this flaky scenario I'm starting a new build and I print if the method worked ok or not, but I let the test run either way. Because the command is working properly, just that the environment is sometimes different because of the nature of the file.( I don't know if I explained this quite right, I hope so.).

> ThIs highlights why it is wrong to prevent new builds from being canceled.

I'm not exclude this status in the command, only Complete,Failed,Cancelled. Now the code base doesn't take care of the `New` status, I know. I will bring it up at the scrum meeting, because we had a talk about this and we said we should make this first work for Pending/Running, since New builds are handled differently.