software/kvm: Fix NBD handling.

Close the NBD socket when testing it so it won't mess up qemu.

/reviewed-on nexedi/slapos!516

software/kvm/buildout.hash.cfg

@@ -59,7 +59,7 @@ md5sum = 2036bf145f472f62ef8dee5e729328fd
 
 [template-kvm-run]
 filename = template/template-kvm-run.in
-md5sum = 9e40246b4bc4f968f0631016c939b014
+md5sum = c8ca875bf246997137552538ab9d8b1a
 
 [template-kvm-controller]
 filename = template/kvm-controller-run.in

software/kvm/template/template-kvm-run.in

@@ -359,6 +359,8 @@ for nbd_ip, nbd_port in nbd_list:
       print 'Warning : Nbd is not available.'
     else:
       # NBD is available
+      # We close the NBD socket else qemu won't be able to use it apparently
+      s.close()
       kvm_argument_list.extend([
           '-drive',
           'file=nbd:[%s]:%s,media=cdrom' % (nbd_ip, nbd_port)])