Correct JUnit notification for background steps

The background steps are copied in the ExecutionUnitRunner for each
scenario in a feature with background. This is done to make them unique
for each scenario, so that the JUnit notification later will not be
ambiguous. When the background steps are executed, it is the original
ones that are executed. Therefore the background steps need to be
'converted' from the original steps to the copies made earlier, when
performing the actual JUnit notifications for an execution unit
(scenario).
Merge branch 'junit-notify-on-background-steps' of https://github.com/brasmusson/cucumber-jvm into brasmusson-junit-notify-on-background-steps
Fix compilation problem. Closes #659, #660
Merge branch 'brasmusson-junit-notify-on-background-steps'