qemu: do not support non-network disks without -drive
qemu: do not support non-network disks without -drive

QEMU added -drive in 2007, and NBD in 2008.  Both appeared first in
release 0.10.0.  Thus the code to support network disks without -drive
is dead, and in fact it incorrectly escapes commas.  Drop it.

Signed-off-by: Paolo Bonzini <69d3ebcf5ee4e7f05a50dc23cd96655b730804b4@redhat.com>

shugaoye/libvirt,jardasgit/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,libvirt/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,nertpinx/libvirt,rlaager/libvirt,zippy2/libvirt,crobinso/libvirt,agx/libvirt,elmarco/libvirt,fabianfreyer/libvirt,shugaoye/libvirt,andreabolognani/libvirt,elmarco/libvirt,taget/libvirt,jfehlig/libvirt,cbosdo/libvirt,jfehlig/libvirt,olafhering/libvirt,cbosdo/libvirt,zhlcindy/libvirt-1.1.4-maintain,elmarco/libvirt,datto/libvirt,olafhering/libvirt,olafhering/libvirt,crobinso/libvirt,jardasgit/libvirt,shugaoye/libvirt,eskultety/libvirt,zhlcindy/libvirt-1.1.4-maintain,andreabolognani/libvirt,nertpinx/libvirt,cbosdo/libvirt,nertpinx/libvirt,eskultety/libvirt,rlaager/libvirt,fabianfreyer/libvirt,agx/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,taget/libvirt,crobinso/libvirt,andreabolognani/libvirt,datto/libvirt,VenkatDatta/libvirt,eskultety/libvirt,zippy2/libvirt,libvirt/libvirt,zhlcindy/libvirt-1.1.4-maintain,libvirt/libvirt,shugaoye/libvirt,jardasgit/libvirt,cbosdo/libvirt,zippy2/libvirt,shugaoye/libvirt,jfehlig/libvirt,taget/libvirt,zippy2/libvirt,agx/libvirt,eskultety/libvirt,libvirt/libvirt,fabianfreyer/libvirt,datto/libvirt,agx/libvirt,agx/libvirt,datto/libvirt,VenkatDatta/libvirt,cbosdo/libvirt,VenkatDatta/libvirt,jfehlig/libvirt,rlaager/libvirt,elmarco/libvirt,taget/libvirt,olafhering/libvirt,crobinso/libvirt,andreabolognani/libvirt,rlaager/libvirt,datto/libvirt,eskultety/libvirt,taget/libvirt,elmarco/libvirt,VenkatDatta/libvirt,nertpinx/libvirt,rlaager/libvirt,zhlcindy/libvirt-1.1.4-maintain,zhlcindy/libvirt-1.1.4-maintain