use mvn instead of run-in-docker (#2821)

Author: wing328

.travis.yml

@@ -121,7 +121,7 @@ script:
   # fail if generators contain tab '\t'
   - /bin/bash ./bin/utils/detect_tab_in_java_class.sh
   # run integration tests defined in maven pom.xml
-  - ./run-in-docker.sh mvn --quiet --batch-mode clean install
+  - mvn --quiet --batch-mode clean install
   - mvn --quiet --batch-mode verify -Psamples
 after_success:
   # push to maven repo