TEST_BUG: update RMI tests to declare othervm explicitly

Currently, all RMI tests are run in othervm mode because of the following lines in jdk/test/TEST.ROOT (edited for brevity):

# Tests that must run in othervm mode
othervm.dirs=... java/rmi ... sun/rmi ...

In addition, the following lines in TEST.ROOT enforce exclusive access (edited for brevity):

# Tests that cannot run concurrently
exclusiveAccess.dirs=java/rmi/Naming

The /othervm declaration should be added to all the RMI tests and the RMI directories removed from the othervm.dirs property. Most, but not all of the RMI tests currently declare /othervm explicitly already. Later, if there are any RMI tests that can run in agentvm mode, the othervm declaration can be removed from them.