MORE Add routines to mount an export in the new Pseudo FS

Improve error message if mounted on export fails

Signed-off-by: Frank S. Filz <ffilzlnx@mindspring.com>
SQUASH Fix get_gsh_export_by_path and get_gsh_export_by_pseudo

Fixup to properly match root path to root export

Signed-off-by: Frank S. Filz <ffilzlnx@mindspring.com>