Fix sourcery-ai review comments

Author: maswin

gateway-ha/src/main/java/io/trino/gateway/ha/router/BaseRoutingManager.java

@@ -25,6 +25,7 @@
 import io.trino.gateway.ha.config.ProxyBackendConfiguration;
 import io.trino.gateway.ha.config.RoutingConfiguration;
 import jakarta.annotation.Nullable;
+import jakarta.annotation.PreDestroy;
 import jakarta.ws.rs.HttpMethod;
 
 import java.net.HttpURLConnection;
@@ -278,6 +279,16 @@ public String load(String queryId)
     private boolean isBackendHealthy(String backendId)
     {
         TrinoStatus status = backendToStatus.getOrDefault(backendId, TrinoStatus.UNKNOWN);
+        if (status == TrinoStatus.UNKNOWN) {
+            log.warn("Backend health for '%s' is UNKNOWN and not tracked.", backendId);
+            return false;
+        }
         return status == TrinoStatus.HEALTHY;
     }
+
+    @PreDestroy
+    public void shutdown()
+    {
+        executorService.shutdownNow();
+    }
 }