run-ha-soak.sh's sequential mode waited for full 3-of-3 reconvergence
between rounds 2+ but had no equivalent wait before round 1's first
kill. A slow cold-start election could let the kill land before
config-push reached both standbys, leaving them at config tag=0 --
ha_on_primary_ctrl_fd_rdhup's voter-only guard then correctly refuses
to let an unconfigured standby self-elect, producing a false "no
primary elected" round-1 failure. Adds node_config_tag/
cluster_config_converged/wait_for_initial_config_convergence,
mirroring the existing reconvergence-wait's polling style, and gates
sequential mode's round 1 on it.
Rongsong Shen
4d2c90389f