test: Don't fail with IndexError when arp output is unexpected
test: Don't fail with IndexError when arp output is unexpected

Closes #3036
Reviewed-by: Peter <a316049dd34607c62d4611d63ab22a6454add223@redhat.com>

mareklibra/cockpit,mvollmer/cockpit,FireDrunk/cockpit,arilivigni/cockpit,arilivigni/cockpit,haiyangd/cockpit_view,petervo/cockpit,matobet/cockpit,cockpituous/cockpit,xhad/cockpit,andreasn/cockpit,Scribery/cockpit,andreasn/cockpit,cockpit-project/cockpit,jscotka/cockpit,moraleslazaro/cockpit,jscotka/cockpit,FireDrunk/cockpit,mareklibra/cockpit,arilivigni/cockpit,larsu/cockpit,moraleslazaro/cockpit,SotolitoLabs/cockpit,xhad/cockpit,deryni/cockpit,sgallagher/cockpit,stefwalter/cockpit,martinpitt/cockpit,larskarlitski/cockpit,moraleslazaro/cockpit,dperpeet/cockpit,andreasn/cockpit,FireDrunk/cockpit,jscotka/cockpit,mareklibra/cockpit,vanloswang/cockpit,vanloswang/cockpit,harishanand95/cockpit,andreasn/cockpit,dperpeet/cockpit,garrett/cockpit,larskarlitski/cockpit,andreasn/cockpit,harishanand95/cockpit,stefwalter/cockpit,Scribery/cockpit,andreasn/cockpit,andreasn/cockpit,mareklibra/cockpit,vanloswang/cockpit,stefwalter/cockpit,mareklibra/cockpit,sgallagher/cockpit,garrett/cockpit,larskarlitski/cockpit,cockpit-project/cockpit,michalskrivanek/cockpit,petervo/cockpit,martinpitt/cockpit,xhad/cockpit,mvollmer/cockpit,arilivigni/cockpit,stefwalter/cockpit,arilivigni/cockpit,martinpitt/cockpit,jscotka/cockpit,SotolitoLabs/cockpit,larskarlitski/cockpit,harishanand95/cockpit,matobet/cockpit,moraleslazaro/cockpit,michalskrivanek/cockpit,harishanand95/cockpit,dperpeet/cockpit,larskarlitski/cockpit,larsu/cockpit,deryni/cockpit,SotolitoLabs/cockpit,deryni/cockpit,moraleslazaro/cockpit,dperpeet/cockpit,sgallagher/cockpit,mvollmer/cockpit,harishanand95/cockpit,michalskrivanek/cockpit,michalskrivanek/cockpit,xhad/cockpit,SotolitoLabs/cockpit,cockpit-project/cockpit,haiyangd/cockpit_view,vanloswang/cockpit,dperpeet/cockpit,petervo/cockpit,mareklibra/cockpit,cockpituous/cockpit,xhad/cockpit,jscotka/cockpit,petervo/cockpit,vanloswang/cockpit,matobet/cockpit,arilivigni/cockpit,michalskrivanek/cockpit,SotolitoLabs/cockpit,haiyangd/cockpit_view,larsu/cockpit,mvollmer/cockpit,michalskrivanek/cockpit,sgallagher/cockpit,martinpitt/cockpit,dperpeet/cockpit,Scribery/cockpit,xhad/cockpit,larsu/cockpit,garrett/cockpit,Scribery/cockpit,larsu/cockpit,cockpituous/cockpit,dperpeet/cockpit,matobet/cockpit,deryni/cockpit,petervo/cockpit,haiyangd/cockpit_view,arilivigni/cockpit,matobet/cockpit,vanloswang/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,sgallagher/cockpit,larskarlitski/cockpit,matobet/cockpit,Scribery/cockpit,FireDrunk/cockpit,sgallagher/cockpit,deryni/cockpit,SotolitoLabs/cockpit,sgallagher/cockpit,Scribery/cockpit,deryni/cockpit,cockpituous/cockpit,stefwalter/cockpit,michalskrivanek/cockpit,vanloswang/cockpit,haiyangd/cockpit_view,garrett/cockpit,petervo/cockpit,larskarlitski/cockpit,cockpituous/cockpit,jscotka/cockpit,cockpit-project/cockpit,xhad/cockpit,Scribery/cockpit,cockpituous/cockpit,garrett/cockpit,mvollmer/cockpit,SotolitoLabs/cockpit,mareklibra/cockpit,stefwalter/cockpit,stefwalter/cockpit,larsu/cockpit,petervo/cockpit,FireDrunk/cockpit,martinpitt/cockpit,cockpit-project/cockpit,deryni/cockpit,harishanand95/cockpit,harishanand95/cockpit