fix actions urls when on action or field traverser

[jensens]

URLs in actions menu pointed to form/actions/fields if on form/actions. now fixed.

[mauritsvanrees]

I think this needs an upgrade step.

Also, I wonder if this has caused Travis test failures. The Travis job for this PR did not finish. Seems a bit unlikely though.
See test failures in this new job today:
https://travis-ci.org/github/collective/collective.easyform/jobs/718885432

I see the tests on the master branch are not run after merging a PR. In the Travis settings, I have now activated 'Build pushed branches'. I guess that was the problem. I have triggered a build.

[mauritsvanrees]

@jensens Does this PR actually fix anything? I cannot reproduce the problem.
When I use easyform 3.0.1, so the release before this change, and run bootstrap-py3.sh (Python 3.7) and create a site, the urls are fine.

• I create a form.
• I go to the Fields action.
• From there I go to the Actions action
• Then to the saved data action. (This does not show anything, but you did some fixes for that later.)

I can click around what I like, going to a different action or the same action, it all works.
What does not work is when I manually add a slash at the end of the url, so: actions/. Then the urls are broken, and your fix would help. But the urls don't have slashes at the end.

Did you see this go wrong on a different Plone or Python version?