systemd: ensure autofs4 and ipv6 are included

Systemd tries to load this modules very early.
Even though they are not strictly required it it is a good
thing to have them around.

[Edited-by: Harald Hoyer: moved to installkernel() ]

modules.d/98systemd/module-setup.sh

@@ -19,6 +19,10 @@ depends() {
     return 0
 }
 
+installkernel() {
+    instmods autofs4 ipv6
+}
+
 # called by dracut
 install() {
     local _mods