Add assumtion on OpenJDK for tests that build on JCE

This patch adds an assumption that OpenJDK is used in some of the tests.
OpenJDK detection utility also added. By specifying -Dcloudstack.jce.enabled=true in the test parameters the OpenJDK detection can be overridden.

Signed-off-by: Laszlo Hornyak <laszlo.hornyak@gmail.com>