Methods annotated with BeforeClass and AfterClass must be static

If a method like https://github.com/infinispan/infinispan/blob/41fcb0d689547870d37736f960eefff4361c40ed/integrationtests/compatibility-mode-it/src/test/java/org/infinispan/it/compatibility/EndpointInteroperabilityTest.java#L83 is not static, the tests results tends to report wrong values.

The repository here https://github.com/diegolovison/testng-reporter demonstrate this issue.

We should update the testng version to be latest one as well. In this time, it is 6.14.3. If we do not update from 6.9.9 the tests will continue passing.

Also, we are using arquilian so this https://github.com/arquillian/arquillian-core/issues/170 issue should be fixed as well.