Handle malformed MIME header in workhorse
Overview
In gitlab-com/gl-infra/production#17066 (closed) we've seen errors like handleFileUploads: extract files from multipart: no api response: status 401
which ends up returning 500 errors.
As suggested in gitlab-com/gl-infra/production#17066 (comment 1632638812) we aren't handling the ProctocolError
so we don't don't return a 400 error.
Edited by Steve Xuereb