[FIXED JENKINS-21739] links to Robot Framework files are now valid for jobs residing inside folders

Links to robot framework report files were invalid (404) when the job was inside a folder (from CloudBees Folder plugin).

For example, instead of:
/job/my_folder/my_job/3446/robot/report/report.html
... we should get:
/job/my_folder/job/my_job/3446/robot/report/report.html

This very simple fix works for all kinds of jobs, given Run.getUrl() provides the right path we need: verified with trivial job, matrix axis, item within a folder. All tests pass.

Could you please consider applying it to the main branch?