Add the -json_topo flag to vtcombo: vttest proto definition of the topology, encoded in json format
Add the -json_topo flag to vtcombo: vttest proto definition of the topology, encoded in json format

Signed-off-by: Simon Engledew <b7bfd6f11fd05fb2bf1757c6a3407b2a598e57c3@github.com>

mahak/vitess,vitessio/vitess,mahak/vitess,vitessio/vitess,vitessio/vitess,mahak/vitess,vitessio/vitess,vitessio/vitess,vitessio/vitess,vitessio/vitess,vitessio/vitess,mahak/vitess,mahak/vitess,mahak/vitess,mahak/vitess,mahak/vitess