Bug#1126699: dbus.dep-fixer run script does not correctly check for existing service definitions

[S. Osipiuk]

The logic in the patch will still try to start a service that's been marked 
with an override even if it doesn't depend on dbus. In *theory* this should be 
harmless because the service *should* have been started earlier because of the 
override, and starting *should* be idempotent, but it still makes this script 
function outside its scope. It shouldn't be touching non-dbus-dependent stuff.