RMIClassLoader does not support the unloading of its classes

The RMIClassLoader holds a hash table mapping codebase URLs to instances of
RMIClassLoader objects. Strong references are used to point to the class loader
instances, so classes loaded through an RMIClassLoader will never get unloaded,
because the class loader itself has its cache that also strongly references the
classes loaded through it (unless, of course, *all* references to the
sun.rmi.server.RMIClassLoader class are gone from the VM, which is a less likely case).