test(ha-commit-barrier-rollout): RED tests for config barrier (task 5.1)
6 RED carriers pinning the three configAck defects (previous-tag acks
count, n_active==0 success shortcut, no-self-count denominator) and the
push/upgrade failure path (logged-only result, unconditional success
ACK + restart). 2 sanctioned pins (single-member, success-unchanged).
Behavior-preserving signature change: push_config_to_standbys gains
acked_out (return still legacy push count; 7 call sites NULL'd,
body-diff verified). 29/6 in group; no collateral failures.
Rongsong Shen
9cdeba5816