Gracefully handle Kafka connection issues

[jonas]

Failure to resolve a Kafka broker will crash a job

Caused by: org.apache.kafka.common.config.ConfigException: DNS resolution failed for url in bootstrap.servers: broker-1.kafka.mesos:6000
	at org.apache.kafka.common.utils.ClientUtils.parseAndValidateAddresses(ClientUtils.java:38)
	at org.apache.kafka.clients.producer.KafkaProducer.<init>(KafkaProducer.java:189)
	at org.apache.kafka.clients.producer.KafkaProducer.<init>(KafkaProducer.java:129)
	at com.mediative.amadou.monitoring.KafkaMessagingSystem.<init>(KafkaMessagingSystem.scala:26)
	at com.mediative.amadou.monitoring.MessagingSystem$.create(MessagingSystem.scala:33)
	at com.mediative.amadou.SparkRunner.<init>(SparkRunner.scala:140)
	at com.mediative.mpn.brain.dataflow.jobs.national.National$.<init>(National.scala:14)
	at com.mediative.mpn.brain.dataflow.jobs.national.National$.<clinit>(National.scala)
	... 1 more