Use OrderedDict to guarantee order

Note:
> Changed in version 3.7: Dictionary order is guaranteed to be
> insertion order. This behavior was an implementation detail of
> CPython from 3.6.

cdist/exec/util.py

@@ -22,6 +22,7 @@
 import subprocess
 import os
 from tempfile import TemporaryFile
+from collections import OrderedDict
 
 import cdist
 import cdist.configuration
@@ -201,7 +202,7 @@ def resolve_conf_dirs(configuration, add_conf_dirs):
         conf_dirs.extend(add_conf_dirs)
 
     # Remove duplicates.
-    conf_dirs = list(dict.fromkeys(conf_dirs))
+    conf_dirs = list(OrderedDict.fromkeys(conf_dirs))
     return conf_dirs