Link-local address on Dhcp6Client has wrong prefix length

Change-Id: Icc83a22f4e638e10b5f8594b3bdb51de540f5785
diff --git a/trellis/trellislib.py b/trellis/trellislib.py
index 1a9d626..8cf3c6c 100644
--- a/trellis/trellislib.py
+++ b/trellis/trellislib.py
@@ -58,9 +58,7 @@
 
     def config(self, **kwargs):
         super(Dhcp6Client, self).config(**kwargs)
-        self.cmd('ip addr flush dev %s' % self.defaultIntf())
-        linkLocalAddr = mac_to_ipv6_linklocal(kwargs['mac'])
-        self.cmd('ip -6 addr add dev %s scope link %s' % (self.defaultIntf(), linkLocalAddr))
+        self.cmd('ip -4 addr flush dev %s' % self.defaultIntf())
         self.cmd('dhclient -q -6 -nw -pf %s -lf %s %s' % (self.pidFile, self.leaseFile, self.defaultIntf()))
 
     def terminate(self, **kwargs):