Add init container to wasmcloud host to wait on NATS connectivity

[joonas]

Right now the wasmcloud host container can come up before the sidecar NATS leaf is up and running, which results in the wasmcloud host crashing and restarting for a few times until the NATS leaf is ready.

We should instead just wait for the NATS connectivity before we start up the host, which is what an init container is used for.