vm: Disable initrd-time QEMU networking for VM images.

Fixes <http://bugs.gnu.org/24943>.
Reported by dian_cecht@zoho.com.

* gnu/system/vm.scm (system-qemu-image)[initrd]: Remove
 #:qemu-networking? #t.
(virtualized-operating-system): Likewise

gnu/system/vm.scm

@@ -317,7 +317,6 @@ (define file-systems-to-keep
               (initrd (lambda (file-systems . rest)
                         (apply base-initrd file-systems
                                #:virtio? #t
-                               #:qemu-networking? #t
                                rest)))
 
               ;; Force our own root file system.
@@ -386,7 +385,6 @@ (define user-file-systems
               (apply base-initrd file-systems
                      #:volatile-root? #t
                      #:virtio? #t
-                     #:qemu-networking? #t
                      rest)))
 
     ;; Disable swap.