Merge PR #26541 into master

* refs/pull/26541/head:
	msg/async: guard protocol Interceptor with preprocessor variable
	cmake: add UNIT_TESTS_BUILD preprocessor var based on WITH_TESTS cmake var
	test/msgr: remove test_msgr2 unused test
	msg/async: msgr2: resolve reconnect races
	test/msgr: msgr2 unit tests using the protocol interceptor WIP
	msg/async: Protocol interceptor infrastructure

Reviewed-by: Sage Weil <sage@redhat.com>