Timer triggered pipelines are not scheduled on a standby server

* This commit fixes an issue with
  #5220 which expected the server to be
  active before scheduling the timer triggered pipelines. With BC addon
  remains active on startup and on TimerSchduler initialization and
  later turns inactive on load of the BC jar.
* Turning of scheduling timer triggered pipelines for standby server by relying
  on the SystemEnvironment 'go.server.mode'.

Author: maheshp

base/src/main/java/com/thoughtworks/go/util/SystemEnvironment.java

@@ -857,6 +857,10 @@ public boolean isProductionMode() {
         return GO_SERVER_MODE.getValue().equalsIgnoreCase("production");
     }
 
+    public boolean isServerInStandbyMode() {
+        return GO_SERVER_MODE.getValue().equalsIgnoreCase("standby");
+    }
+
     public boolean isReAuthenticationEnabled() {
         return REAUTHENTICATION_ENABLED.getValue();
     }

common/src/test/java/com/thoughtworks/go/util/SystemEnvironmentTest.java

@@ -522,4 +522,13 @@ public void shouldReturnFalseIfBooleanSystemPropertyIsAnythingButYOrTrue() {
         System.setProperty("go.config.repo.gc.periodic", "some-value");
         assertThat(new SystemEnvironment().get(SystemEnvironment.GO_CONFIG_REPO_PERIODIC_GC), is(false));
     }
+
+    @Test
+    public void shouldBeInStandByModeIfGoServerModeIsSetToStandby() {
+        assertFalse(new SystemEnvironment().isServerInStandbyMode());
+
+        System.setProperty("go.server.mode", "StandBy");
+
+        assertTrue(new SystemEnvironment().isServerInStandbyMode());
+    }
 }

server/src/main/java/com/thoughtworks/go/server/service/TimerScheduler.java

@@ -74,7 +74,10 @@ public TimerScheduler(Scheduler scheduler, GoConfigService goConfigService,
     }
 
     public void initialize() {
-        if (!systemEnvironment.isServerActive()) return;
+        if (systemEnvironment.isServerInStandbyMode()) {
+            LOG.info("GoCD server in 'standby' mode, skipping scheduling timer triggered pipelines.");
+            return;
+        }
 
         scheduleAllJobs(goConfigService.getAllPipelineConfigs());
         goConfigService.register(this);

server/src/test-fast/java/com/thoughtworks/go/server/service/TimerSchedulerTest.java

@@ -188,10 +188,10 @@ public void shouldRescheduleTimerTriggerPipelineWhenItsConfigChanges() throws Sc
     }
 
     @Test
-    public void shouldNotScheduleJobsOnAnInactiveServer() {
+    public void shouldNotScheduleJobsForAServerInStandbyMode() {
         TimerScheduler timerScheduler = new TimerScheduler(scheduler, goConfigService, null, null, systemEnvironment);
 
-        when(systemEnvironment.isServerActive()).thenReturn(false);
+        when(systemEnvironment.isServerInStandbyMode()).thenReturn(true);
 
         timerScheduler.initialize();