authPrompt: Do not enable sensitivity if retries are disallowed

Set the sensitivity of the UI according to the canRetry parameter and thus
if no more logins are allowed don't take any input.

Fixes #311


(cherry picked from commit 8f848925f6cdae0d96c355faa8acc2b0d45ab16c)

js/gdm/authPrompt.js

@@ -242,11 +242,11 @@ var AuthPrompt = new Lang.Class({
         this.emit('prompted');
     },
 
-    _onVerificationFailed() {
+    _onVerificationFailed(userVerifier, canRetry) {
         this._queryingService = null;
         this.clear();
 
-        this.updateSensitivity(true);
+        this.updateSensitivity(canRetry);
         this.setActorInDefaultButtonWell(null);
         this.verificationStatus = AuthPromptStatus.VERIFICATION_FAILED;
     },

js/gdm/util.js

@@ -562,7 +562,7 @@ var ShellUserVerifier = new Lang.Class({
             }
         }
 
-        this.emit('verification-failed');
+        this.emit('verification-failed', canRetry);
     },
 
     _onConversationStopped(client, serviceName) {