In
22abd785eb s3: implement reading and writing of metadata #111
The reading information of objects was refactored to use the
s3.HeadObjectOutput structure.
Unfortunately the code branch with `--s3-no-head` was not tested
otherwise this panic would have been discovered.
This shows that this is path is not integration tested, so this adds a
new integration test.
Fixes#6322
440d0cd179