This commit overhauls several of the tests that interact with an
MBeanServer with the goal of increasing the reliability of these tests.
- MBeanClientInterceptorTests now uses JUnit "assumptions" instead of
preemptively returning from test methods, thus allowing such methods
to be properly marked as "ignored" instead of "passed".
- MBeanClientInterceptorTests now uses JUnit's support for expected
exceptions where appropriate.
- MBeanClientInterceptorTests and RemoteMBeanClientInterceptorTests now
use Spring's SocketUtils to find an available TCP port when starting
an MBeanServer instead of aborting the tests when the default JMX
port is not available.
Issue: SPR-12601