The following commands:

* backup-mariadb
* recover-dump
* check-mariadb-backups
* remote-backup-mariadb

And the following config files:

* backup.cnf
* remote_backup.cnf

Are now fully documented on man pages, so one can check its
syntax on the hosts where they are installed, without having
to run --help.

Bug: T138562
Change-Id: I081f2390112076e50cb84232fb0a3a2c28c5748a