Start readiness service after http is started (elastic#136729) (elastic#136924)

The readiness service indicates when ES is ready to receive
external http requests. Yet the service does not actually check http has
been started. This commit moves the starting the readiness service to
after http has been started. Note that adding a direct dependency
between ReadinessService and HttpServerTransport would be complicated,
so the "dependency" is achieved by starting readiness almost at the end
of node startup.

Author: rjernst

docs/changelog/136729.yaml

@@ -0,0 +1,5 @@
+pr: 136729
+summary: Start readiness service after http is started
+area: Infra/Node Lifecycle
+type: bug
+issues: []

server/src/main/java/org/elasticsearch/node/Node.java

@@ -277,9 +277,6 @@ public Node start() throws NodeValidationException {
         logger.info("starting ...");
         pluginLifecycleComponents.forEach(LifecycleComponent::start);
 
-        if (ReadinessService.enabled(environment)) {
-            injector.getInstance(ReadinessService.class).start();
-        }
         injector.getInstance(MappingUpdatedAction.class).setClient(client);
         injector.getInstance(IndicesService.class).start();
         injector.getInstance(IndicesClusterStateService.class).start();
@@ -408,6 +405,9 @@ public void onTimeout(TimeValue timeout) {
         }
 
         injector.getInstance(HttpServerTransport.class).start();
+        if (ReadinessService.enabled(environment)) {
+            injector.getInstance(ReadinessService.class).start();
+        }
 
         if (WRITE_PORTS_FILE_SETTING.get(settings())) {
             TransportService transport = injector.getInstance(TransportService.class);