Fix compile and test issues on stable-2.16

Gerrit has dropped the support for setting the LogThreshold
so remove its use in the multi-site plugin.

Also fix the JSON serialisation for strings.

Change-Id: Ic2b823ecbcd6044547da4f48ad24e9d27d93aee2
diff --git a/src/main/java/com/googlesource/gerrit/plugins/multisite/forwarder/GsonParser.java b/src/main/java/com/googlesource/gerrit/plugins/multisite/forwarder/GsonParser.java
index cd14b93..ddc184a 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/multisite/forwarder/GsonParser.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/multisite/forwarder/GsonParser.java
@@ -75,7 +75,11 @@
         break;
       case Constants.PROJECT_LIST:
       default:
-        json = gson.toJson(key);
+        if (key instanceof String) {
+          json = (String) key;
+        } else {
+          json = gson.toJson(key);
+        }
     }
     return json;
   }
diff --git a/src/test/java/com/googlesource/gerrit/plugins/multisite/kafka/consumer/EventConsumerIT.java b/src/test/java/com/googlesource/gerrit/plugins/multisite/kafka/consumer/EventConsumerIT.java
index cbd192d..98c4679 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/multisite/kafka/consumer/EventConsumerIT.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/multisite/kafka/consumer/EventConsumerIT.java
@@ -19,7 +19,6 @@
 
 import com.google.gerrit.acceptance.AbstractDaemonTest;
 import com.google.gerrit.acceptance.GerritConfig;
-import com.google.gerrit.acceptance.LogThreshold;
 import com.google.gerrit.acceptance.NoHttpd;
 import com.google.gerrit.acceptance.UseLocalDisk;
 import com.google.gerrit.extensions.api.changes.ReviewInput;
@@ -73,7 +72,6 @@
 import org.testcontainers.containers.KafkaContainer;
 
 @NoHttpd
-@LogThreshold(level = "INFO")
 @UseLocalDisk
 public class EventConsumerIT extends AbstractDaemonTest {
   public static final String GERRIT_CONFIG_KEY = "gerrit.installModule";