tech debt: nats connection establishment

[butonic]

While working on #2049 I noticed that we have multiple ways of instantiating nats connections:

• go micro store
• native nats client
  • in various ways
• in reva
• in opencloud
• in health checks

We rely on nats and should embrace it without minio in between. It not only allows us to weaken the dependency on micro but also reuse the real nats connection for health checks. Currently, we try to create a new connection ... which says nothing about the actual connections.