Remove one add_dockerfile "unit test"
Remove one add_dockerfile "unit test"

The test used to unit-test both the add_labels_in_df and add_dockerfile
plugins at the same time. Even by the loosest possible definition of the
words, that is not a unit test.

The same functionality is tested by test_adddockerfile_nvr_from_labels.

Signed-off-by: Adam Cmiel <1217f9865bd733d1bcad0d0d64be310272c5592c@redhat.com>

projectatomic/atomic-reactor,fr34k8/atomic-reactor,fr34k8/atomic-reactor,projectatomic/atomic-reactor