add default flannel configuration for cni

cluster/images/hyperkube/Dockerfile

@@ -68,6 +68,9 @@ ADD https://storage.googleapis.com/kubernetes-release/easy-rsa/easy-rsa.tar.gz /
 # Copy the cni folder into /opt/
 COPY cni /opt/cni
 
+# Copy overlay configuration to default directory
+COPY cni-conf /etc/cni/net.d
+
 # Create symlinks for each hyperkube server
 # TODO: this is unreliable for now (e.g. running "/kubelet" panics)
 # Also, it doesn't work for other architectures

cluster/images/hyperkube/cni-conf/10-containernet.conf

+{
+  "name": "containernet",
+  "type": "flannel",
+  "delegate": {
+        "bridge": "cni0",
+        "mtu": 1450,
+        "isDefaultGateway": true
+    }
+}

cluster/images/hyperkube/cni-conf/99-loopback.conf

+{
+    "type": "loopback"
+}