Write setup-complete marker on non-manager nodes

so-boot-highstate.service was never enabled outside managers: only the
manager branch of so-setup called mark_setup_complete, so the marker its
service.enabled gates on never existed on sensors, search nodes, receivers,
etc.

Move the marker state into salt.minion.boot_highstate as the sole owner
within a highstate. Non-managers never apply salt.minion during setup, so
reaching it means setup is done and the marker is unconditional -- this also
heals already-installed nodes. Managers keep the legacy startup_states gate,
since they do highstate mid-setup.

Also add the marker to setup.virt for salt-cloud guests (replacing the
startup_states line removed in fabecb82) and to so-setup's non-manager branch.

setup/so-setup

@@ -833,6 +833,7 @@ if ! [[ -f $install_opt_file ]]; then
 		check_sos_appliance
 		drop_install_options
 		hypervisor_local_states
+		mark_setup_complete
 		verify_setup
 	fi