DERBY-6733: Implement an MBean for monitoring caches

Add test that verifies that a SecurityException is raised if the MBean
is accessed by code that hasn't been granted permission to monitor the
engine.

git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/trunk@1626682 13f79535-47bb-0310-9956-ffa450edef68