- New scylla node always send application_state::RPC_READY = false when
the node boots and send application_state::RPC_READY = true when cql
server is up
- Old scylla node that does not support the application_state::RPC_READY
never has application_state::RPC_READY in the endpoint_state, we can
only think their cql server is up, so we return true here if
application_state::RPC_READY is not present