unhandled exceptions in checks.d initialization kill the agent

[clutchski]

They should just log an exception, note the error for the info command and continue without that check. A silly example from our sobotka queue check:

    sys.exit(main())
  File "/usr/bin/dd-agent", line 227, in main
    agent.run(config=agentConfig)
  File "/usr/bin/dd-agent", line 100, in run
    checksd = load_check_directory(agentConfig)
  File "/usr/share/datadog/agent/config.py", line 669, in load_check_directory
    agentConfig=agentConfig)
  File "/usr/share/datadog/agent/checks.d/dd.py", line 10, in __init__
    port=int(init_config['redis_port']),
ValueError: invalid literal for int() with base 10: '6380asdf'