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
Fix LargeClusterStressTest to create clustered caches and check the data
perf testing hacks