light-controller: handle exception if cannot reach CI server

[jasaw]

Pi was configured to talk to Jenkins CI, but getting connection refused exception and dies.

Traceback (most recent call last):
File "/storage/build-lights/light-controller/light_controller.py", line 162, in
lc = LightController()
File "/storage/build-lights/light-controller/light_controller.py", line 112, in init
self.ci = importlib.import_module('ci_server.' + ci_server_type).Source(**ci_server_conf)
File "/storage/build-lights/light-controller/ci_server/jenkins.py", line 26, in init
self.J = Jenkins(url)
File "/usr/local/lib/python2.7/dist-packages/jenkinsapi/jenkins.py", line 59, in init
JenkinsBase.init(self, baseurl, poll=not lazy)
File "/usr/local/lib/python2.7/dist-packages/jenkinsapi/jenkinsbase.py", line 35, in init
self.poll()
File "/usr/local/lib/python2.7/dist-packages/jenkinsapi/jenkinsbase.py", line 59, in poll
data = self._poll(tree=tree)
File "/usr/local/lib/python2.7/dist-packages/jenkinsapi/jenkins.py", line 64, in _poll
if not tree else tree)
File "/usr/local/lib/python2.7/dist-packages/jenkinsapi/jenkinsbase.py", line 79, in get_data
response = requester.get_url(url, params)
File "/usr/local/lib/python2.7/dist-packages/jenkinsapi/utils/requester.py", line 109, in get_url
return requests.get(self._update_url_scheme(url), **requestKwargs)
File "/usr/lib/python2.7/dist-packages/requests/api.py", line 60, in get
return request('get', url, **kwargs)
File "/usr/lib/python2.7/dist-packages/requests/api.py", line 49, in request
return session.request(method=method, url=url, **kwargs)
File "/usr/lib/python2.7/dist-packages/requests/sessions.py", line 457, in request
resp = self.send(prep, **send_kwargs)
File "/usr/lib/python2.7/dist-packages/requests/sessions.py", line 569, in send
r = adapter.send(request, **kwargs)
File "/usr/lib/python2.7/dist-packages/requests/adapters.py", line 407, in send
raise ConnectionError(err, request=request)
requests.exceptions.ConnectionError: ('Connection aborted.', error(111, 'Connection refused'))

[surpher]

Pi was configured and tested against a local Jenkins CI in local network.
Pi was then moved to a new location in a different network with limited connectivity where the configured Jenkins CI server is not reachable anymore.
When booting up the Pi, light_controller and light_controller_server fail to launch (as evident from Supervisor dashboard ..:9001).
Restarting the controllers through Supervisor dashboard shows 500 Error.