The patch for MDEV-15530 incorrectly added a column in the middle of SHOW
SLAVE STATUS output. This is wrong, as it breaks backwards compatibility
with existing applications and scripts. In this case, it even broke
mariadb-dump, which is included in the server source tree!

Revert the incorrect change, putting the new Replicate_Rewrite_DB at the end
of SHOW SLAVE STATUS output.

Add a testcase for the mariadb-dump --dump-slave wrong output problem. Also
add a testcase rpl.rpl_show_slave_status to hopefully prevent any future
incorrect additions to SHOW SLAVE STATUS.
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>