added route for getting routers list locally

inventory_provider/routes/testing.py

 import collections
 import json
+import os
 import re
 
 from flask import Blueprint, Response, jsonify, current_app
@@ -219,6 +220,12 @@ def get_netconf(hostname):
     return msg
 
 
+@routes.route("routers-list", methods=['GET', 'POST'])
+def routers_from_config_dir():
+    with open(os.environ['FAKE_ROUTERS_FILE']) as f:
+        return Response(f.read(), mimetype="text.plain")
+
+
 @routes.route("latchdb", methods=['GET', 'POST'])
 def latch_db():
     config = current_app.config["INVENTORY_PROVIDER_CONFIG"]