Update the ProtocolVersion implementation

This change updates the implementation of the ProtocolVersion
struct, bringing it inline with the current struct style. All
uses of the struct have been updated to reflect these changes,
as have the struct unit tests.

kmip/services/server/session.py

@@ -176,7 +176,7 @@ class KmipSession(threading.Thread):
             self._logger.warning("Failure parsing request message.")
             self._logger.exception(e)
             response = self._engine.build_error_response(
-                contents.ProtocolVersion.create(1, 0),
+                contents.ProtocolVersion(1, 0),
                 enums.ResultReason.INVALID_MESSAGE,
                 "Error parsing request message. See server logs for more "
                 "information."