Manage octavia health manager worker through openstack_service worker

Change-Id: Idfa7feb9157cdf12af9641be10c8eb8478930f15
Closes-Bug: #1886747

ansible/roles/octavia/templates/octavia.conf.j2

@@ -62,6 +62,9 @@ bind_ip = {{ octavia_network_interface_address }}
 heartbeat_key = insecure
 controller_ip_port_list = {% for host in groups['octavia-health-manager'] %}{{ 'octavia_network' | kolla_address(host) | put_address_in_context('url') }}:{{ octavia_health_manager_port }}{% if not loop.last %},{% endif %}{% endfor %}
 
+stats_update_threads = {{ openstack_service_workers }}
+health_update_threads = {{ openstack_service_workers }}
+
 [controller_worker]
 amp_boot_network_list = {{ octavia_amp_boot_network_list }}
 amp_image_tag = amphora