Enable DHCPv6 client

Set `DHCP=yes` in `/etc/systemd/network/80-dhcp.network` to start both
DHCPv4 and DHCPv6 clients. This provides IPv6 for networks using DHCPv6
without RA.

It should not have much effect of networks with working RA since the
`IPv6AcceptRA` option is enabled by default for these connections anyway.

images/basic.sh

@@ -17,7 +17,7 @@ function pre() {
 Name=eth*
 
 [Network]
-DHCP=ipv4
+DHCP=yes
 EOF
 }
 

images/common.sh

@@ -19,7 +19,7 @@ EOF
 Name=eth*
 
 [Network]
-DHCP=ipv4
+DHCP=yes
 EOF
 
   # install vagrant ssh key