### Motivation
Fixes#5994:
If the proxy service comes up before the brokers are up and reachable there will be HTTP 403 when running `bin/pulsar-admin` commands from inside the proxy pod.
The proxy will also not be able to connect to the brokers when data is pushed through binary port with the following error:
```bash
Caused by: org.apache.pulsar.broker.service.BrokerServiceException$PersistenceException: org.apache.bookkeeper.mledger.ManagedLedgerException: Not enough non-faulty bookies available
... 14 more
Caused by: org.apache.bookkeeper.mledger.ManagedLedgerException: Not enough non-faulty bookies available
22:11:07.633 [pulsar-web-32-6] INFO org.eclipse.jetty.server.RequestLog - 172.17.0.6 - - [24/Jan/2020:22:11:07 +0000] "PUT /admin/v2/persistent/public/functions/assignments HTTP/1.1" 500 2528 "-" "Pulsar-Java-v2.5.0" 280
```
#### Workaround:
Restart the proxy pods once brokers pods are running
#### Proposed solution:
Hold off starting of the proxies until at least one broker is reachable in the cluster.
### Modifications
Changes are inside `proxy-deployment.yaml` helm template file that defines a new init container before proxy is started. The init container waits until broker is reachable using the nslookup on the broker service with a sleep of 30 seconds between retries and up to number of brokers times.
Alternative solution that doesn't always work was `'until nslookup broker-service; sleep 2; done;', but 403 would still sometimes (could have been a fluke, but I saw it happening once).
### Verifying this change
1) Follow the instructions on how deploying helm and run:
`helm install pulsar --values pulsar/values-mini.yaml ./pulsar/`.
2) Wait until all the services are up and running.
3) Connect to proxy pod and run `bin/pulsar-admin broker-stats monitoring-metrics` - no 403 or permission errors should arise
4) Set up tenant, namespace
5) Push data into a topic - No errors in the proxy logs and client is able to push data into cluster through proxies
56e0d05e25