Merge pull request #29181 from Random-Liu/add-doc-for-node-e2e-kubenet-flag

Automatic merge from submit-queue

Node E2E: Add document for node e2e --disable-kubenet flag.

Address the comment https://github.com/kubernetes/kubernetes/pull/28213#discussion_r70137103.
Offline discussed with @vishh, we should document the `--disable-kubenet` flag in node e2e test.

hack/make-rules/test-e2e-node.sh

@@ -127,10 +127,15 @@ else
     sudo -v || exit 1
   fi
 
+  # If the flag --disable-kubenet is not set, set true by default.
+  if ! [[ $test_args =~ "--disable-kubenet" ]]; then
+    test_args="$test_args --disable-kubenet=true"
+  fi
   # Test using the host the script was run on
   # Provided for backwards compatibility
+  set -x
   "${ginkgo}" --focus=$focus --skip=$skip "${KUBE_ROOT}/test/e2e_node/" --report-dir=${report} \
-    -- --alsologtostderr --v 2 --node-name $(hostname) --disable-kubenet=true --build-services=true \
-    --start-services=true --stop-services=true "$test_args"
+    -- --alsologtostderr --v 2 --node-name $(hostname) --build-services=false \
+    --start-services=true --stop-services=true $test_args
   exit $?
 fi