Don't test kotlin if not in jdk8

tests.sh

@@ -226,8 +226,13 @@ build_java_with_conformance_tests() {
   # This local installation avoids the problem caused by a new version not yet in Maven Central
   cd java/bom && $MVN install
   cd ../..
-  cd java && $MVN test && $MVN install
-  cd util && $MVN package assembly:single
+  cd java/core && $MVN test && $MVN install
+  cd ../lite && $MVN test && $MVN install
+  cd ../util && $MVN package assembly:single
+  if [ "$version" == "jdk8" ]; then
+    cd ../kotlin && $MVN test && $MVN install
+    cd ../kotlin-lite && $MVN test && $MVN install
+  fi
   cd ../..
   cd conformance && make test_java && cd ..
 }