Feature: vmq-admin reset command

[ioolkos]

Only "empty" independent VerneMQ nodes should join a cluster. A VerneMQ node with pre-existing state should not join a cluster.

To make this more explicit, we should have a documented reset command (similar to the RabbitMQ reset command). For Verne, this means moving or deleting the releases' data directories (usually all dirs under /var/lib/vernemq) and rebooting. Resetting without re-booting is probably not necessary (and would require the implementation of certain handler processes).
A reset command would free users from having to figure out where state is stored on a node.

Technically, a non-empty node is currently not prevented from joining a cluster. A joining node could also do a self-check and prevent the join attempt, in case it finds previous state. The self-check is dependent on the configured sync protocol.