Deb: Make libmariadb3 Breaks+Replaces libmariadbclient18 so upgrade pass

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.

debian/control

@@ -49,7 +49,9 @@ Conflicts: mariadb-galera-server-10.0 (<< 10.0.5),
            mariadb-server-5.3,
            mariadb-server-5.5 (<< 5.5.33),
            libmariadbclient18 (<< 10.2.0)
-Replaces: libmysqlclient19,
+Breaks: libmariadbclient18 (<< ${source:Version})
+Replaces: libmariadbclient18 (<< ${source:Version}),
+          libmysqlclient19,
           libmysqlclient20
 Provides: libmysqlclient19,
           libmysqlclient20