subscriptions: Cleanup register operation
subscriptions: Cleanup register operation

Put the running of the subscription-manager process in its own
operation function, and return a promise.

This separates updating the UI out from running the command.

Reviewed-by: Dominik Perpeet <f7830b2723a5db4fc185058b06cfab4b89a38da9@redhat.com>

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