fix(java): Pass missing integration test flags to native image test commands (#1309)

Author: dzou

synthtool/gcp/templates/java_library/.kokoro/build.sh

@@ -71,7 +71,7 @@ integration)
     ;;
 graalvm)
     # Run Unit and Integration Tests with Native Image
-    mvn -ntp -Pnative -Penable-integration-tests test
+    mvn -B ${INTEGRATION_TEST_ARGS} -ntp -Pnative -Penable-integration-tests test
     RETURN_CODE=$?
     ;;
 samples)