[dynect|dns] Fixes exception behavior for 307's

This PR fixes exception behavior when Dynect returns a 307 with a job number.  At some point, the behavior of wait_for.rb was changed to raise an exception if duration > timeout. The exception raised by core supersedes the one raised in Dynect/dns.rb that includes the job number, which is then lost.  The job number is now returned as part of the exception.

Original Issue:
https://github.com/fog/fog/issues/575

Commit implementing original behavior:
https://github.com/fog/fog/commit/7ba6df8f1494c98849dbdc25bdc34a1f4605ee47