[EXT] Added removing the data folder for `cluster_name` to make sure the testing cluster starts green

Since the "store=memory" and "gateway=none" options have been removed, the data were left between
cluster restarts, and the default index settings with 1 replica prevented the "green" health,
timeouting the cluster launch.

Related: e6f8111
[EXT] Make sure the `cluster_name` argument is not empty/dangerous in test cluster launcher

Related: ef05b21