Update the DirectoryServer class so that it resets the JDK logger whenever the
server shuts down.  This is necessary to prevent an exception when performing
an in-core restart (as described in issue #1289) or potentially other cases in
which the server may need to be started multiple times in the same JVM (e.g.,
as in issue #1495).

Note that this has the potential to interfere with applications which embed
OpenDS and also use the JDK logger.  If they ever shut down OpenDS, then it
could deregister the parent application's loggers as well.  The only way for us
to fix this is to rewrite our loggers so they don't use the JDK logging
framework at all.