Print errors on stderr in install/update

If we're not doing fancy ui, print errors on stderr. This was biting me
in some tests where I'd like to grep for some strings in the stderr
output.

app/flatpak-cli-transaction.c

@@ -494,7 +494,7 @@ operation_error (FlatpakTransaction            *transaction,
       redraw (self);
     }
   else
-    g_print ("\r%-*s\n", self->table_width, text);
+    g_printerr ("\r%-*s\n", self->table_width, text);
 
   if (!non_fatal && self->stop_on_first_error)
     return FALSE;