The package libmariadbclient18 contains the dialog.so plugin, which also
the new libmariadb3 ships. As they both use the exact same path the latter
must be marked as a with Breaks and Replaces relations ship.

Note: This fix is conservative hack for stable releases 10.2 and 10.3.
In 10.4, the development release at the time, we will clean up how the
libmariadb3 packaging and it's -compat packages are done to match that
what is done in downstream Debian official.