Enabling parsing of EnqueuedTimeUtc given its new serialization format

We've encountered an issue with some of our production code using this library for service bus work. It appears that the library's unit tests fail with the same error as our production code, which leads me to believe that the serialization format of the EnqueuedTimeUtc header has changed from that specified in the following doc: http://msdn.microsoft.com/en-us/library/windowsazure/hh780742.aspx

Note that other DateTime headers (e.g. ScheduledEnqueueTimeUtc) appear to still retain the old format.

It looks as though this changed happened some time around the 10th of this month, from our logs. Our fix is to treat the parsing of this header slightly differently to the rest. This had the knock-on effect of causing the scenario integration tests to incorrectly fail--the ScenarioHelper.compare_messages method has been modified accordingly.