[CAT-780] fixed Back Button Behaviour in Object View

fixed behaviour and adapted tests

testrun:
https://jenkins.catrob.at/view/All-Categories/view/Catroid-multi-job/job/Catroid-Multi-Job-Custom-Branch/1990/
Is there no other way than passing the fragment instance to the dialog?

Sidenote: We really shouldn't be using the constructors of the fragments and dialog fragments if we ever want to support rotation in our app.