tests/network: use ping -6 instead of ping6

The latter is a symlink to the former, and the symlink is not present in
Arch.

Author: marmarek

qubes/tests/integ/network_ipv6.py

@@ -36,7 +36,7 @@
 class VmIPv6NetworkingMixin(VmNetworkingMixin):
     test_ip6 = "2000:abcd::1"
 
-    ping6_cmd = "ping6 -W 1 -n -c 1 {target}"
+    ping6_cmd = "ping -6 -W 1 -n -c 1 {target}"
 
     def setUp(self):
         super(VmIPv6NetworkingMixin, self).setUp()