Don't follow redirections in Jenkins responses

There is no need to follow redirections in Jenkins responses. For example when invoking a build, Jenkins redirects browser to job's page, but there is no need to read the page in jenkinsapi.

I have used http codes 200 and 302, because I wasn't sure if all versions of Jenkins responded by 302 to all modified actions. There was also needed to add a delay after stopping a build/invocation to let Jenkins actually stop the build before it was safe to check if the build is not running... I'm not sure if this is actually not the test-specific requirement and the delay should be rather placed there instead of in the stop() methods.