agents: monitoring: init: check for config file
agents: monitoring: init: check for config file

- setup:run() will always process.exit(). note that fact and remove the
  else statement to unest the main init logic

- check to ensure the config file exists in main init code, otherwise we
  backtrace if the config file is missing. This logic was lost in
  aff197b33d73e49d9

christopherjwang/rackspace-monitoring-agent,virgo-agent-toolkit/rackspace-monitoring-agent,cp16net/virgo-base,kaustavha/rackspace-monitoring-agent,AlphaStaxLLC/rackspace-monitoring-agent,virgo-agent-toolkit/rackspace-monitoring-agent,cp16net/virgo-base,AlphaStaxLLC/rackspace-monitoring-agent,christopherjwang/rackspace-monitoring-agent,cp16net/virgo-base,cp16net/virgo-base,kaustavha/rackspace-monitoring-agent,cp16net/virgo-base