Document another workaround for a vagrant failure
Originally created by @segfault on #16144 (Redmine)
When I try to build Tails, vagrant sometimes fails with
Initialization parameters must be an attributes hash, got NilClass nil (ArgumentError)
Restarting libvirtd
fixes this, as suggested
here.
We should add this to our Known issues and workarounds section in contribute/build.
Feature Branch: bugfix/16144-document-workaround