…OfProject

The jenkinsClient inside JenkinsService comes from JenkinsConfig, wihch, as of
spinnaker#1130, uses SpinnakerRetrofitErrorHandler.
Therefore, the getBuilds calls inside the try/catch block inside processBuildsOfProject
throws a SpinnakerServerException.

spinnaker#1130 updated the 'should continue processing other
builds from a master even if one or more build fetches fail' test to throw a
SpinnakerServerException with a RetrofitError as its cause instead of a RuntimeException
with a RetrofitError as its cause.  With spinnaker/kork#1110, the
SpinnakerServerException no longer has a RetrofitError as its cause.  It has the "mock
root cause" exception as its cause.  But, because
spinnaker/kork#1110 adds a url attribute to
SpinnakerServerException, the cause is no longer necessary for including a url in the
"Error communicating with jenkins" log message, and this commit updates the logic
accordingly.

…Spec

remove unused runtimeException and rename retrofitEx since it's no longer a retrofitEx