Fix deactivating MFA on user accounts (#2797)

api/user.go

@@ -2277,6 +2277,9 @@ func generateMfaQrCode(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 
 	w.Header().Del("Content-Type") // Content-Type will be set automatically by the http writer
+	w.Header().Set("Cache-Control", "no-cache")
+	w.Header().Set("Pragma", "no-cache")
+	w.Header().Set("Expires", "0")
 	w.Write(img)
 }
 

webapp/components/user_settings/user_settings_security.jsx

@@ -139,10 +139,9 @@ class SecurityTab extends React.Component {
         );
     }
     deactivateMfa() {
-        const data = {};
-        data.activate = false;
-
-        Client.updateMfa(data,
+        Client.updateMfa(
+            '',
+            false,
             () => {
                 this.props.updateSection('');
                 AsyncClient.getMe();