[PR #4494/da4fe01b backport][3.35] Avoid automatic encoding for fixture server

[patchback]

This is a backport of PR #4494 as merged into main (da4fe01).

This is a fix that was added to pulp-smash but is missing here.

See more here:

pulp/pulp-smash#1309
pulp/pulp-smash@a18afe9

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It also speeds up local testing (at least in pulp_deb) because it will no longer try to verify the encoding of extracted archive files 4 times before failing. Which looks like this:

9d1d6ce495d7 Giving up download_wrapper(...) after 4 tries (pulpcore.exceptions.validation.DigestValidationError: A file located at the url http://127.0.0.1:59071/debian-update/dists/ragnarok/jotunheimr/binary-armeb/Packages.gz failed validation due to checksum. Expected 'c3d96859b1edfce90bfb47928dad84b0616d9322d6df5a8a8a704d361ab78930', Actual '6a5079388629eacffc797c85b9083d1153db91cf9bc124be4f4dac33fa0647a3')
9d1d6ce495d7 pulp [af77c374-19b8-4c87-9120-70d9e4e82331]: backoff:ERROR: Giving up download_wrapper(...) after 4 tries (pulpcore.exceptions.validation.DigestValidationError: A file located at the url http://127.0.0.1:59071/debian-update/dists/ragnarok/jotunheimr/binary-armeb/Packages.gz failed validation due to checksum. Expected 'c3d96859b1edfce90bfb47928dad84b0616d9322d6df5a8a8a704d361ab78930', Actual '6a5079388629eacffc797c85b9083d1153db91cf9bc124be4f4dac33fa0647a3')
9d1d6ce495d7 pulp [af77c374-19b8-4c87-9120-70d9e4e82331]: pulp_deb.app.tasks.synchronizing:INFO: Digest for artifact with relative_path='dists/ragnarok/jotunheimr/binary-armeb/Packages.gz' not matched. Ignored