Emanuele Aina authored Sep 09, 2019 and Denis Pynkin committed Sep 10, 2019

Work around issues with the APT downloader corrupting files and
causing "Hash Sum Mismatch" errors.

A typical occurence is like:

    Get:97 https://repositories.apertis.org/apertis v2019pre/target amd64 libsystemd-dev amd64 240-5co3bb1 [317 kB]
    Err:97 https://repositories.apertis.org/apertis

 v2019pre/target amd64 libsystemd-dev amd64 240-5co3bb1
      Hash Sum mismatch
      Hashes of expected file:
       - SHA256:39654a35430ef132537880d67cd906bc958e1282e5e2d267e0d9ea96198c3649
       - SHA1:3d358b67b624162c4737a619de078cb8ae6091f6 [weak]
       - MD5Sum:c9da96eacf456df58bd564ab587a7a22 [weak]
       - Filesize:317116 [weak]
      Hashes of received file:
       - SHA256:caf4eacc492e6e67651c6d4ace49ee2800c3166e8d630cddd35b87c94042f655
       - SHA1:9690ac45a5282cc04fcbfc6fc3d2ac2e4c6fa375 [weak]
       - MD5Sum:33dcb5800d6e0c3c4d86f0e37c3d134e [weak]
       - Filesize:317116 [weak]
      Last modification reported: Tue, 21 May 2019 14:59:26 +0000

The failures rate goes from hard-to-reproduce to reliably-fails.

Downloading the affected files with `wget` or `curl` has not reproduced
the issue, and only `apt` seems affected. The issue has hit jobs on
Jenkins as well as pipelines on GitLab, and from time to time people
have been able to remporarily reproduce it locally in image builder
Docker container.

From the captured network traffic it seems that HTTP pipelining is
involved, disabling its usage in APT so far prevented the issue to come
up in cases where it was reproducible.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>