[Hawkular-dev] agent PR needs peer review

PR: https://github.com/hawkular/hawkular-agent/pull/161 JIRA: https://issues.jboss.org/browse/HWKAGENT-63 When the agent starts up, if it doesn't know its tenant ID yet, it has to ask Hawkular-Accounts for it. But if the Hawkular Server isn't up yet, the agent will die during startup. This PR addresses that issue by having the agent perform some retries. This will give a bit more fault-tolerance to the agent should a hawkular server be down when the agent starts up.