ISPN-4938 Infinispan Commons Util package is not in generated Javadoc

* Also fixed import in interface
ISPN-4886 SingleNodeJdbcStoreIT.testForcedShutdown and
testNormalShutdown random failures

* Made sure we put the same byte as the test consistently
JavaDoc: multiline code examples are mangled
ISPN-3743

Ignore some of the errors that can be thrown by a node while stopping:
IllegalStateException and NullPointerException.