[fix] robot tests ++ set default value for server http protocol version

searx/settings_robot.yml

     secret_key : "ultrasecretkey" # change this!
     base_url : False
     image_proxy : False
+    http_protocol_version : "1.0"
 
 ui:
     themes_path : ""

searx/webapp.py

 
 # serve pages with HTTP/1.1
 from werkzeug.serving import WSGIRequestHandler
-WSGIRequestHandler.protocol_version = "HTTP/{}".format(settings['server']['http_protocol_version'])
+WSGIRequestHandler.protocol_version = "HTTP/{}".format(settings['server'].get('http_protocol_version', '1.0'))
 
 static_path, templates_path, themes =\
     get_themes(settings['ui']['themes_path']