Ignore unreliable KieScannerMemoryTest

We have KieScannerMemoryTest test class which should check for memory leaks. However this test class is unreliable, because it depends at the number of steps during which memory raises. However with unpredictable GC behaviour, this sometimes reports false negatives. Therefore we should @Ignore it. It could help debugging memory leaks when used locally, but in automated test runs, it should be disabled.