PLT-3237 Update displayed config values in admin console after saving (#3506)

* Reloaded admin console data when settings are saved

* Fixed attempting to save an invalid config setting overwriting the stored config

webapp/components/admin_console/external_service_settings.jsx

@@ -17,11 +17,6 @@ export default class ExternalServiceSettings extends AdminSettings {
         this.getConfigFromState = this.getConfigFromState.bind(this);
 
         this.renderSettings = this.renderSettings.bind(this);
-
-        this.state = Object.assign(this.state, {
-            segmentDeveloperKey: props.config.ServiceSettings.SegmentDeveloperKey,
-            googleDeveloperKey: props.config.ServiceSettings.GoogleDeveloperKey
-        });
     }
 
     getConfigFromState(config) {
@@ -31,6 +26,13 @@ export default class ExternalServiceSettings extends AdminSettings {
         return config;
     }
 
+    getStateFromConfig(config) {
+        return {
+            segmentDeveloperKey: config.ServiceSettings.SegmentDeveloperKey,
+            googleDeveloperKey: config.ServiceSettings.GoogleDeveloperKey
+        };
+    }
+
     renderTitle() {
         return (
             <h3>