tools/test.py: Fix classpath options

Fix bootstrap and system classpath command line options to make all
tests pass again.

Signed-off-by: Pekka Enberg <penberg@kernel.org>
tests: Switch to 1.6 for JNI tests

It's mostly cosmetic but switch to 1.6 for JNI tests for consistency
with rest of the test suite.

Signed-off-by: Pekka Enberg <penberg@kernel.org>