Use JUnit 3.8.2 under CQ 3589

Use JUnit 3.8.2 under CQ 3589

CQ 3589 was submitted to request permission to use JUnit 3.8.2
from Orbit.  We don't redistribute JUnit but we compile against it
and do redistribute a test support JAR (org.eclipse.jgit.junit)
that would depend upon it if someone were to develop their own
application code and also wish to write unit tests with JUnit.

Change-Id: I23b1f23e064224363585ec2f5dd62a0b4d28fb5b
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>