[cherry-pick][branch-2.9] cherry-pick #17736 problem and DnsResolverTest license header#18640

congbobo184 merged 8 commits into

branch-2.9apache/pulsar:branch-2.9from

congbo/cherry-pick-2.9/fix_#17736_problem_MessageCumulativeAckTest_mockapache/pulsar:congbo/cherry-pick-2.9/fix_#17736_problem_MessageCumulativeAckTest_mockCopy head branch name to clipboard