util: Check/ignore already disabled event
util: Check/ignore already disabled event

If the event is already disabled, then don't bother with setting it
disabled again.  Causes unnecessary error on systems that don't support
the feature anyway.

VenkatDatta/libvirt,andreabolognani/libvirt,datto/libvirt,taget/libvirt,andreabolognani/libvirt,jfehlig/libvirt,jardasgit/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,andreabolognani/libvirt,VenkatDatta/libvirt,nertpinx/libvirt,andreabolognani/libvirt,jardasgit/libvirt,jardasgit/libvirt,taget/libvirt,VenkatDatta/libvirt,eskultety/libvirt,jardasgit/libvirt,datto/libvirt,taget/libvirt,zippy2/libvirt,jardasgit/libvirt,crobinso/libvirt,nertpinx/libvirt,libvirt/libvirt,fabianfreyer/libvirt,libvirt/libvirt,taget/libvirt,fabianfreyer/libvirt,zippy2/libvirt,zippy2/libvirt,eskultety/libvirt,crobinso/libvirt,olafhering/libvirt,jfehlig/libvirt,olafhering/libvirt,crobinso/libvirt,olafhering/libvirt,datto/libvirt,eskultety/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt,olafhering/libvirt,crobinso/libvirt,zippy2/libvirt,libvirt/libvirt,datto/libvirt,taget/libvirt,fabianfreyer/libvirt,eskultety/libvirt,libvirt/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,datto/libvirt,eskultety/libvirt,VenkatDatta/libvirt,nertpinx/libvirt