Python3: Fix using dictionary keys()

It will throw TypeError when you try to operate on
dict.keys() like a list in python3.
ref:https://docs.python.org/3/library/stdtypes.html#dictionary-view-objects

Change-Id: I3f1173e74ddd589f3d363597bd1562299f92e93d

sahara/utils/patches.py

@@ -79,7 +79,7 @@ def patch_minidom_writexml():
         writer.write(indent + "<" + self.tagName)
 
         attrs = self._get_attributes()
-        a_names = attrs.keys()
+        a_names = list(attrs.keys())
         a_names.sort()
 
         for a_name in a_names: