common: Work around misconfigured systemd not passing a socket
common: Work around misconfigured systemd not passing a socket

Previously this would just kill the process. We should instead
produce an intelligible message, and not necessarily dump core.

https://bugzilla.gnome.org/show_bug.cgi?id=746339

Fixes #1931
Reviewed-by: Marius Vollmer <bb11c6e942c5cc765df5f04da146b3198127a7a3@redhat.com>

denysvitali/cockpit,mareklibra/cockpit,denysvitali/cockpit,dperpeet/cockpit,andreasn/cockpit,sgallagher/cockpit,xhad/cockpit,moolitayer/cockpit,FireDrunk/cockpit,larsu/cockpit,moraleslazaro/cockpit,dperpeet/cockpit,haiyangd/cockpit_view,Armstrong1992/cockpit,xhad/cockpit,moolitayer/cockpit,moraleslazaro/cockpit,larsu/cockpit,jscotka/cockpit,matobet/cockpit,moraleslazaro/cockpit,harishanand95/cockpit,cockpituous/cockpit,mareklibra/cockpit,cockpituous/cockpit,cockpit-project/cockpit,andreasn/cockpit,Armstrong1992/cockpit,zigitax/cockpit,denysvitali/cockpit,Armstrong1992/cockpit,andreasn/cockpit,nmav/cockpit,petervo/cockpit,cockpit-project/cockpit,sgallagher/cockpit,moraleslazaro/cockpit,fridex/cockpit,moolitayer/cockpit,martinpitt/cockpit,vanloswang/cockpit,andreasn/cockpit,SotolitoLabs/cockpit,evol262/cockpit,matobet/cockpit,vbatts/cockpit,michalskrivanek/cockpit,vbatts/cockpit,Scribery/cockpit,Scribery/cockpit,vbatts/cockpit,petervo/cockpit,michalskrivanek/cockpit,michalskrivanek/cockpit,arilivigni/cockpit,harishanand95/cockpit,cockpit-project/cockpit,haiyangd/cockpit_view,darioajr/cockpit,michalskrivanek/cockpit,cockpit-project/cockpit,dperpeet/cockpit,michalskrivanek/cockpit,cockpituous/cockpit,fridex/cockpit,nmav/cockpit,vanloswang/cockpit,Thermionix/cockpit,arilivigni/cockpit,michalskrivanek/cockpit,harishanand95/cockpit,evol262/cockpit,larsu/cockpit,matobet/cockpit,stefwalter/cockpit,fridex/cockpit,maxamillion/cockpit,moolitayer/cockpit,firebitsbr/cockpit,arilivigni/cockpit,martinpitt/cockpit,darioajr/cockpit,fridex/cockpit,SotolitoLabs/cockpit,jscotka/cockpit,deryni/cockpit,cockpituous/cockpit,fridex/cockpit,andreasn/cockpit,arilivigni/cockpit,nmav/cockpit,larskarlitski/cockpit,mvollmer/cockpit,jscotka/cockpit,mareklibra/cockpit,darioajr/cockpit,denysvitali/cockpit,darioajr/cockpit,larskarlitski/cockpit,larskarlitski/cockpit,larskarlitski/cockpit,firebitsbr/cockpit,cockpituous/cockpit,moolitayer/cockpit,evol262/cockpit,evol262/cockpit,martinpitt/cockpit,mvollmer/cockpit,sgallagher/cockpit,larskarlitski/cockpit,deryni/cockpit,harishanand95/cockpit,SotolitoLabs/cockpit,SotolitoLabs/cockpit,jscotka/cockpit,firebitsbr/cockpit,larskarlitski/cockpit,zigitax/cockpit,garrett/cockpit,netzvieh/cockpit,martinpitt/cockpit,nmav/cockpit,moraleslazaro/cockpit,andreasn/cockpit,deryni/cockpit,haiyangd/cockpit_view,netzvieh/cockpit,jscotka/cockpit,maxamillion/cockpit,Thermionix/cockpit,FireDrunk/cockpit,deryni/cockpit,larsu/cockpit,martinpitt/cockpit,matobet/cockpit,vbatts/cockpit,SotolitoLabs/cockpit,petervo/cockpit,SotolitoLabs/cockpit,sgallagher/cockpit,petervo/cockpit,netzvieh/cockpit,firebitsbr/cockpit,stefwalter/cockpit,stefwalter/cockpit,zigitax/cockpit,fridex/cockpit,xhad/cockpit,arilivigni/cockpit,maxamillion/cockpit,mvollmer/cockpit,mareklibra/cockpit,petervo/cockpit,maxamillion/cockpit,dperpeet/cockpit,moraleslazaro/cockpit,sgallagher/cockpit,haiyangd/cockpit_view,Scribery/cockpit,Scribery/cockpit,Thermionix/cockpit,cockpit-project/cockpit,vanloswang/cockpit,Armstrong1992/cockpit,garrett/cockpit,mareklibra/cockpit,Scribery/cockpit,Thermionix/cockpit,larsu/cockpit,arilivigni/cockpit,mvollmer/cockpit,vanloswang/cockpit,netzvieh/cockpit,haiyangd/cockpit_view,maxamillion/cockpit,FireDrunk/cockpit,Thermionix/cockpit,dperpeet/cockpit,larsu/cockpit,garrett/cockpit,vbatts/cockpit,firebitsbr/cockpit,FireDrunk/cockpit,vanloswang/cockpit,Scribery/cockpit,cockpituous/cockpit,jscotka/cockpit,harishanand95/cockpit,sgallagher/cockpit,nmav/cockpit,garrett/cockpit,Armstrong1992/cockpit,FireDrunk/cockpit,stefwalter/cockpit,xhad/cockpit,deryni/cockpit,vanloswang/cockpit,zigitax/cockpit,netzvieh/cockpit,xhad/cockpit,moraleslazaro/cockpit,stefwalter/cockpit,mvollmer/cockpit,harishanand95/cockpit,mareklibra/cockpit,Thermionix/cockpit,matobet/cockpit,deryni/cockpit,michalskrivanek/cockpit,harishanand95/cockpit,netzvieh/cockpit,Scribery/cockpit,matobet/cockpit,arilivigni/cockpit,darioajr/cockpit,stefwalter/cockpit,vbatts/cockpit,evol262/cockpit,zigitax/cockpit,dperpeet/cockpit,andreasn/cockpit,petervo/cockpit,xhad/cockpit,deryni/cockpit,mareklibra/cockpit,dperpeet/cockpit,petervo/cockpit,evol262/cockpit,SotolitoLabs/cockpit,garrett/cockpit,larskarlitski/cockpit,denysvitali/cockpit,sgallagher/cockpit,vanloswang/cockpit,stefwalter/cockpit,xhad/cockpit