Investigate connection pool reconnect when Kafka not yet available

[jfallows]

Use zilla-demos streampay with connection pool enabled to attempt to reproduce.

Steps to reproduce

1. git clone https://github.com/aklivity/zilla-demos/tree/main/streampay
2. Go to streampay/stack and edit stack.yaml file by removing , "-Pzilla.binding.kafka.client.connection.pool=false"]
   3 Follow the readme to start the stack

**Expected behaviour **
Zilla starts successfully and starts receiving messages and streampay UI works

**Actual behaviour **
zilla prints

 zilla-streampay-demo-api:kafka_asyncapi_client.$composite-kafka_api.kafka_client0 [18/Jul/2024:06:31:39 +0000] BINDING_KAFKA_AUTHORIZATION_FAILED Unable to authenticate client with identity (user)

and doesn't receive any message hence streampay app doesn't work

[jfallows]

Reproducing this issue is a race condition on startup of the stack.

During stack startup, we also create the redpanda user used by zilla to authenticate access.

If zilla attempts to connect before the user is created and authentication fails, then the zilla connection pool does not attempt to reconnect.