Fix inconsistencies in session auth failures

The spice session implementation can retry authentication on its own,
whereas the vnc session needs to tear down the session and re-connect in
order to retry a failed authentication. This results in the following
inconsistent behavior:

VNC session:
 - emits a 'session-auth-failed' signal when the client does not support
   a particular authentication type (i.e.: a non-recoverable error)
Spice session:
- emits a 'session-auth-failed' signal when user enters an incorrect
  password, and immediately retries auth internally

VNC session:
 - emits a 'session-auth-refused' error when user enters an invalid
   password (i.e.: a recoverable error)
Spice Session:
- never emits a 'session-auth-refused' signal

Because of these differences, the VirtViewerApp code to handle authentication
failures is a bit confusing and difficult to maintain. To fix this issue, make
both the spice and VNC sessions emit the same signal when similar errors occur.
We use the new session API added in the last commit to determine whether the
session supports automatic retries so we know how to handle the signal.

src/virt-viewer-app.c

@@ -1488,7 +1488,7 @@ static void virt_viewer_app_cancelled(VirtViewerSession *session,
 }
 
 
-static void virt_viewer_app_auth_refused(VirtViewerSession *session G_GNUC_UNUSED,
+static void virt_viewer_app_auth_refused(VirtViewerSession *session,
                                          const char *msg,
                                          VirtViewerApp *self)
 {
@@ -1496,6 +1496,15 @@ static void virt_viewer_app_auth_refused(VirtViewerSession *session G_GNUC_UNUSE
     int ret;
     VirtViewerAppPrivate *priv = self->priv;
 
+    if (virt_viewer_session_can_retry_auth(session)) {
+        virt_viewer_app_simple_message_dialog(self,
+                                              _("Unable to authenticate with remote desktop server at %s: %s\n"),
+                                              priv->pretty_address, msg);
+        return;
+    }
+
+    /* if the session implementation cannot retry auth automatically, the
+     * VirtViewerApp needs to schedule a new connection to retry */
     dialog = gtk_message_dialog_new(virt_viewer_window_get_window(priv->main_window),
                                     GTK_DIALOG_MODAL |
                                     GTK_DIALOG_DESTROY_WITH_PARENT,
@@ -1515,7 +1524,6 @@ static void virt_viewer_app_auth_refused(VirtViewerSession *session G_GNUC_UNUSE
         priv->authretry = FALSE;
 }
 
-
 static void virt_viewer_app_auth_failed(VirtViewerSession *session G_GNUC_UNUSED,
                                         const char *msg,
                                         VirtViewerApp *self)

src/virt-viewer-session-spice.c

@@ -617,7 +617,7 @@ virt_viewer_session_spice_main_channel_event(SpiceChannel *channel,
         }
 
         if (self->priv->pass_try > 0)
-            g_signal_emit_by_name(session, "session-auth-failed",
+            g_signal_emit_by_name(session, "session-auth-refused",
                                   error != NULL ? error->message : _("Invalid password"));
         self->priv->pass_try++;