APM Server Logs Errors at Info Level

**Describe the bug**
APM server incorrectly logs error messages at info level.

example log messages (host names are redacted):
```
...
info client/metadata fetching metadata for [apm-6.8.7] from broker :
info Failed to connect to broker :: dial tcp: i/o timeout
info kafka message: client/metadata got error from broker while fetching metadata:%!(EXTRA *net.OpError=dial tcp: i/o timeout)
...
```

**To Reproduce**
- APM server is using Kafka output.
- Kafka brokers were having internal errors due to failure to connect to Zookeeper hosts.
- Kafka brokers were reachable but unable to accept client connection/data.
- APM server is unable to send data to Kafka brokers and log error messages at info level.

**Expected behavior**
I expect these messages to be logged at a warning level or higher.