chore: add dnsPolicy for sample deployment (#498)

Signed-off-by: Jintao Zhang <zhangjintao9020@gmail.com>
diff --git a/samples/deploy/deployment/ingress-controller.yaml b/samples/deploy/deployment/ingress-controller.yaml
index eae43e1..eaca8dd 100644
--- a/samples/deploy/deployment/ingress-controller.yaml
+++ b/samples/deploy/deployment/ingress-controller.yaml
@@ -39,6 +39,7 @@
         tier: backend
     spec:
       hostNetwork: true
+      dnsPolicy: ClusterFirstWithHostNet
       containers:
       - image: apache/apisix-ingress-controller:0.1.0
         imagePullPolicy: IfNotPresent