If you running your Maven installation with a different JDK than JDK 9 you have give the JDK 9 path via the command line:
mvn clean verify -Prun-its -Dinvoker.javaHome=JDK9JAVAHOME
The reason behind this is simply cause Maven JMod Plugin will call jmod tool
of the JDK which is needed to be found. Otherwise none of the
integration tests can work.