modprobe fuse on the CI build machine

To make the swh-fuse CI pass, we need the fuse kernel module loaded in the docker container (and hence its host) when tests are run. Here's an example of failure that happens when that's not the case: https://jenkins.softwareheritage.org/job/DFUSE/job/tests-on-diff/13/console (search for "modprobe fuse" there).

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Migrated from T2654 (view on Phabricator)