debian: Ensure unit tests have a working $HOME
debian: Ensure unit tests have a working $HOME

pbuilder's user has home dir "/nonexistent" in /etc/passwd (so commit
8acf23b9 does not help), so the build fails with lots of

  WARNING: cockpit-bridge: couldn't create runtime dir: /nonexistent/.cache: Permission denied

This could arguably be downgraded to a message as it's not an internal
Cockpit inconsistency, but doing that then results in subsequent
warnings like

  WARNING: cockpit-bridge: couldn't create temporary socket file: No such file or directory

It makes more sense to run the tests with an actually working $HOME
directory, so set one in debian/rules.

Closes #6198
Reviewed-by: Dominik Perpeet <f7830b2723a5db4fc185058b06cfab4b89a38da9@redhat.com>
michalskrivanek/cockpit,andreasn/cockpit,harishanand95/cockpit,mareklibra/cockpit,xhad/cockpit,deryni/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,larsu/cockpit,larskarlitski/cockpit,mareklibra/cockpit,larskarlitski/cockpit,cockpituous/cockpit,dperpeet/cockpit,xhad/cockpit,mvollmer/cockpit,SotolitoLabs/cockpit,deryni/cockpit,harishanand95/cockpit,mareklibra/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,mareklibra/cockpit,garrett/cockpit,larskarlitski/cockpit,larskarlitski/cockpit,Scribery/cockpit,deryni/cockpit,martinpitt/cockpit,stefwalter/cockpit,dperpeet/cockpit,martinpitt/cockpit,deryni/cockpit,michalskrivanek/cockpit,garrett/cockpit,garrett/cockpit,deryni/cockpit,mvollmer/cockpit,stefwalter/cockpit,moraleslazaro/cockpit,dperpeet/cockpit,SotolitoLabs/cockpit,mareklibra/cockpit,garrett/cockpit,dperpeet/cockpit,andreasn/cockpit,andreasn/cockpit,stefwalter/cockpit,andreasn/cockpit,cockpituous/cockpit,harishanand95/cockpit,larsu/cockpit,cockpituous/cockpit,xhad/cockpit,stefwalter/cockpit,mareklibra/cockpit,larskarlitski/cockpit,petervo/cockpit,mvollmer/cockpit,dperpeet/cockpit,larsu/cockpit,michalskrivanek/cockpit,SotolitoLabs/cockpit,michalskrivanek/cockpit,SotolitoLabs/cockpit,cockpit-project/cockpit,martinpitt/cockpit,larskarlitski/cockpit,garrett/cockpit,moraleslazaro/cockpit,Scribery/cockpit,petervo/cockpit,harishanand95/cockpit,martinpitt/cockpit,stefwalter/cockpit,moraleslazaro/cockpit,stefwalter/cockpit,harishanand95/cockpit,stefwalter/cockpit,SotolitoLabs/cockpit,mvollmer/cockpit,deryni/cockpit,Scribery/cockpit,petervo/cockpit,andreasn/cockpit,xhad/cockpit,SotolitoLabs/cockpit,xhad/cockpit,dperpeet/cockpit,harishanand95/cockpit,cockpituous/cockpit,deryni/cockpit,petervo/cockpit,martinpitt/cockpit,harishanand95/cockpit,Scribery/cockpit,cockpituous/cockpit,Scribery/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,petervo/cockpit,cockpit-project/cockpit,andreasn/cockpit,mareklibra/cockpit,larskarlitski/cockpit,xhad/cockpit,moraleslazaro/cockpit,SotolitoLabs/cockpit,michalskrivanek/cockpit,xhad/cockpit,petervo/cockpit,larsu/cockpit,larsu/cockpit,michalskrivanek/cockpit,petervo/cockpit,Scribery/cockpit,larsu/cockpit,dperpeet/cockpit,Scribery/cockpit,michalskrivanek/cockpit,cockpit-project/cockpit,mvollmer/cockpit,andreasn/cockpit