vmTestbase/nsk/jvmti/ClassPrepare/classprep001 should skip events for unexpected classes

vmTestbase/nsk/jvmti/ClassPrepare/classprep001 test requests ClassPrepare event and expects exactly 2 events (for the test interface and then for the test class). But concurrent class loading may cause loading of other classes (for example from java.util.concurrent class).
The test should be ready for the case and skip events from other classes