Increase change screen refresh to 5 mins

Increase default setting of change.updateDelay to facilitate new
Gerrit setups of novice users to scale up even with limited
resources availability.

The old value (30 seconds) was too small and caused problems
of server overloaded by REST API calls.

Change-Id: I68f8adfbb887e7f300e6c53b791570e4b22a5458

Documentation/config-gerrit.txt

@@ -998,7 +998,7 @@ requests per second and requires ~10% CPU.
 +
 If 0 the update polling is disabled.
 +
-Default is 30 seconds.
+Default is 5 minutes.
 
 [[change.allowBlame]]change.allowBlame::
 +

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/config/ServerInfoIT.java

@@ -168,7 +168,7 @@ public class ServerInfoIT extends AbstractDaemonTest {
     assertThat(i.change.largeChange).isEqualTo(500);
     assertThat(i.change.replyTooltip).startsWith("Reply and score");
     assertThat(i.change.replyLabel).isEqualTo("Reply\u2026");
-    assertThat(i.change.updateDelay).isEqualTo(30);
+    assertThat(i.change.updateDelay).isEqualTo(300);
 
     // download
     assertThat(i.download.archives).containsExactly("tar", "tbz2", "tgz", "txz");

gerrit-server/src/main/java/com/google/gerrit/server/config/GetServerInfo.java

@@ -216,7 +216,7 @@ public class GetServerInfo implements RestReadView<ConfigResource> {
     info.replyLabel =
         Optional.ofNullable(cfg.getString("change", null, "replyLabel")).orElse("Reply") + "\u2026";
     info.updateDelay =
-        (int) ConfigUtil.getTimeUnit(cfg, "change", null, "updateDelay", 30, TimeUnit.SECONDS);
+        (int) ConfigUtil.getTimeUnit(cfg, "change", null, "updateDelay", 300, TimeUnit.SECONDS);
     info.submitWholeTopic = Submit.wholeTopicEnabled(cfg);
     return info;
   }