app-client impl assumes client and server share the same filesystem

Some jax-rpc tests using app-client were failing due to JBVFS-17. This however pointed out that our current implementation for app-client is supposed to work only when server and client share the same filesystem (see the referenced forum thread). We should think about something like a buffering virtual file implementation that eagerly reads the referenced resources from the file system before the metadata it is contained in is bound to the JNDI.