[change] Requested changes

- use gettext in management_ip js code
- remove unnecessary _connector_field logic
- fix typo in readme

README.rst

@@ -148,7 +148,7 @@ the administration dashboard.
 Connection App
 ~~~~~~~~~~~~~~
 
-This app enables to controller to utilize various protocols for designated purposes.
+This app enables the controller to utilize various protocols for designated purposes.
 Currently, the default connnection protocols are SNMP and SSH, but the protocol
 mechanism is extensible and custom protocols can be implemented as well.
 

openwisp_controller/config/static/config/js/device.js

@@ -7,6 +7,7 @@ django.jQuery(function ($) {
   // replaces the management ip field with text with the option to edit it
   var ip_input = $(".field-management_ip > div > input");
   var initial_ip = ip_input.val();
+  var management_ip_alt = gettext("Edit");
   ip_input.after(function () {
     ip_input.hide();
     return (
@@ -15,23 +16,35 @@ django.jQuery(function ($) {
       "</span>"
     );
   });
-  $("#management_ip_text").after(
-    '<a id="edit_management_ip"><img src="/static/admin/img/icon-changelink.svg" alt="Edit"></a>'
-  );
+  $("#management_ip_text").after(function () {
+    return (
+      '<a id="edit_management_ip"><img value="edit" src="/static/admin/img/icon-changelink.svg" alt="' +
+      management_ip_alt +
+      '" title="' +
+      management_ip_alt +
+      '"></a>'
+    );
+  });
   $("#edit_management_ip").click(function () {
     var ip_text = $("#management_ip_text");
     var img_element = $("#edit_management_ip > img");
-    if (img_element.attr("alt") === "Edit") {
+    if (img_element.attr("value") === "edit") {
       ip_input.show();
       ip_text.hide();
+      management_ip_alt = gettext("Cancel");
       img_element.attr("src", "/static/admin/img/icon-deletelink.svg");
-      img_element.attr("alt", "Cancel");
+      img_element.attr("value", "cancel");
+      img_element.attr("alt", management_ip_alt);
+      img_element.attr("title", management_ip_alt);
     } else {
       ip_text.show();
       ip_input.hide();
       ip_input.val(initial_ip);
+      management_ip_alt = gettext("Edit");
       img_element.attr("src", "/static/admin/img/icon-changelink.svg");
-      img_element.attr("alt", "Edit");
+      img_element.attr("value", "edit");
+      img_element.attr("alt", management_ip_alt);
+      img_element.attr("title", management_ip_alt);
     }
   });
 });

openwisp_controller/connection/base/models.py

@@ -44,13 +44,6 @@ def clean(self):
         self._validate_connector_schema()
 
     def _get_connector(self):
-        if not hasattr(self, '_connectors'):
-            self._connectors = dict(app_settings.CONNECTORS)
-        try:
-            if self._connectors[self.credentials.connector] == 'SNMP':
-                return self.credentials.connector
-        except AttributeError:
-            pass
         return getattr(self, self._connector_field)
 
     def _validate_connector_schema(self):