Camera2: Fix metadata XML to maintain ordering

Change-Id: I69adfbb1010b5f624d3ee618a1a45e0be510ca31
diff --git a/camera/docs/metadata_helpers.py b/camera/docs/metadata_helpers.py
index 1a01dff..35e9ba4 100644
--- a/camera/docs/metadata_helpers.py
+++ b/camera/docs/metadata_helpers.py
@@ -19,6 +19,7 @@
 """
 
 import metadata_model
+from collections import OrderedDict
 
 _context_buf = None
 
@@ -76,7 +77,7 @@
      not isinstance(node, metadata_model.InnerNamespace):
       raise TypeError("expected node to be a Section or InnerNamespace")
 
-  d = {}
+  d = OrderedDict()
   # remove the 'kinds' from the path between sec and the closest entries
   # then search the immediate children of the search path
   search_path = isinstance(node, metadata_model.Section) and node.kinds \