Revert "repodata: make get_dataset public"
This reverts commit a236b5b95d896b0f40ce1fa3c8fc3eed5195de36.
I overlooked the _repodata.py file and mistakenly made get_dataset
public altough it should never be. Instead some methods for retrieving
the required data from the repodata should've been added. This commit
fixes that.
Signed-off-by: Nils Philippsen <nils@redhat.com>