add autoinst_url and move more functions into basetest

having the functions in basetest allows us to overwrite them in the distribution
and have different logic in the future
move distribution specifics into a new class distribution

we just can't mix global testapi namespace with test specific basetest in perl.
So I split the testapi specific to distribution out of basetest to make namespaces
and responsibilities clearer
Merge pull request #124 from os-autoinst/fix_endless_recursion

Fix endless recursion