Currently we have fixed rate limit logging in the GitHub driver. This
does a rate limit api call after almost each api call to
GibHub. However if the GitHub Enterprise instance doesn't have a rate
limit configured this logging doesn't make sense and costs an
additional network round trip time for every request. Thus make this
configurable and by default enabled to retain the current behavior.
Change-Id: I39762611ff74e2ab1fb277f8e9c32be0673abfa3
Tobias Henkel