Automatic merge from submit-queue (batch tested with PRs 54843, 55810). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
fix testSupport in downwardapi_test
add some code to test plugin.CanSupport function
/sig storage