Restore the fetching of all refs with empty delta

When the FetchOne's delta is empty the fetching should run
with all refs. This fixes a regression introduced by I093ce3a7
when the recover from failed fetch of individual refs has
mistakenly skipped also the all refs fetching.

Change-Id: I3ea2769d7819b2b79ec2d4f2b9514fc91dee7c3e