845622: If an identity certificate has expired, there should be a friendly error message

If an SSL Error is returned, the expiration date on the identity cert is checked
 for expiration. The result is a new type of exception that will be caught in
 Subscription Manager.
Improve logging for rhsmcertd scenarios
Merge branch 'master' into wottop/845622
Merge pull request #49 from candlepin/wottop/845622

845622: If an identity certificate has expired, there should be a friend...