* Tests to see if the file this <code>SmbFile</code> represents
 * exists and is not marked read-only. By default, resources are
 * considered to be read-only and therefore for <code>smb1://</code>,
 * <code>smb1://workgroup/</code>, and <code>smb1://server/</code> resources
 * will be read-only.
 *
 * @return  <code>true</code> if the resource exists is not marked
 *          read-only
 */