Java 8 - consider backporting javassist upgrade to help modules

While implementing Java 8 it was discovered that the javassist library needed an upgrade to fix JUnit powermock tests. The fix was done against master here: https://github.com/openmrs/openmrs-core/commit/e6ba58db5b48c6b63303d373e00fbc7ade60a8d0

It turns out that several modules also use powermock, and run into the same problem when building against Java 8. To prevent having to fix all of the modules, consider backporting the javassist upgrade. All of the modules need to upgrade core to fix Hibernate 4 issues anyway, so may as well upgrade javassist at the same time?