- gitlab.lister: Do not expect gitlab instances to have credentials
Only the main gitlab.com instance supports a rate limit (thus the
credentials need), others do not (as per summer 2018, i did not check today).
gitlab.lister: Break asap when problem exists during fetch info step
Prior to this, when wrong url injection happens (and it happened /o\),
no information is fetched. Because we have a bad input in the first place
(either 404 or 400). This makes for a long debugging session...