Add some additional jvmti-stress skips

These were failing with jvmti-stress. Tests 159 & 649 are failing
due to issues with dexter and test 647 was failing due to using
an unsupported classloader.

Bug: 38344137
Test: ./test/testrunner/testrunner.py --host -j40 --jvmti-stress
Change-Id: I1fea19540f498ada091fc64edcf7187b4af81f79
1 file changed