Stub out kernel-network-modules dracut module

This dumb module includes a ton of useless drivers.  There doesn't seem
to be a way to avoid including it, because it is expressed as a
dependency of the *network* module, and even explicitly omitting the
modules it would include seems to have no effect.

overlay/usr/lib/dracut/modules.d/90kernel-network-modules/module-setup.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/bash
+
+check() {
+    return 255
+}
+
+depends() {
+    return 0
+}
+
+installkernel() {
+    return 0
+}
+
+install() {
+    return 0
+}