MB-7522 Improve test 24-updater-add-more-passive-partitions.t

Verify that toggling partitions between the passive and active
states (and vice-versa) while the updater is running doesn't
lead to crashes, a bad state or data loss.

Change-Id: I565b8e04b38d39b13949ad9aa6ae52e2651e1647
Reviewed-on: http://review.couchbase.org/23893
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>