Fix constants to use environment variables in preference to config files

lib/ansible/constants.py

@@ -124,10 +124,6 @@ def get_config(p, section, key, env_var, default, value_type=None, expand_relati
 def _get_config(p, section, key, env_var, default):
     ''' helper function for get_config '''
     value = default
-    if env_var is not None:
-        env_value = os.environ.get(env_var, None)
-        if env_value is not None:
-            value = env_value
 
     if p is not None:
         try:
@@ -135,6 +131,11 @@ def _get_config(p, section, key, env_var, default):
         except:
             pass
 
+    if env_var is not None:
+        env_value = os.environ.get(env_var, None)
+        if env_value is not None:
+            value = env_value
+
     return to_text(value, errors='surrogate_or_strict', nonstring='passthru')