For Linux service users, (#1236)

* For Linux service users,
use `appdirs.AppDirs().site_data_dir`
instead of `appdirs.AppDirs().user_config_dir

* somewhat important for this to be changed consistently

* need to import os to use it

* travis doesn't like how I was checking in config_dir had been set.

redbot/core/data_manager.py

@@ -1,4 +1,5 @@
 import sys
+import os
 from pathlib import Path
 from typing import List
 import hashlib
@@ -30,7 +31,13 @@ basic_config_default = {
     "CORE_PATH_APPEND": "core"
 }
 
-config_dir = Path(appdirs.AppDirs("Red-DiscordBot").user_config_dir)
+config_dir = None
+appdir = appdirs.AppDirs("Red-DiscordBot")
+if sys.platform == 'linux':
+    if os.getuid() < 1000:
+        config_dir = Path(appdir.site_data_dir)
+if not config_dir:
+    config_dir = Path(appdir.user_config_dir)
 config_file = config_dir / 'config.json'