Sort the Locate matched objects by their creation date

This change updates the PyKMIP server's support for the Locate
operation, sorting the matched objects found by Locate by their
initial date, newest objects first. This matches the KMIP
specification's definition for how Locate results should be
ordered.

kmip/services/server/engine.py

@@ -1773,6 +1773,13 @@ class KmipEngine(object):
 
             managed_objects = managed_objects_filtered
 
+        # Sort the matching results by their creation date.
+        managed_objects = sorted(
+            managed_objects,
+            key=lambda x: x.initial_date,
+            reverse=True
+        )
+
         unique_identifiers = [
             str(x.unique_identifier) for x in managed_objects
         ]