Fixed: Service selection in GA Ticket Action allows multi select (bug#10578).
Squashed commit of the following:

commit 0b41aede7b331c3d9fd42c114a11cfbcfd0def36
Author: s7design <otrs@s7designcreative.com>
Date:   Thu Jun 19 14:00:15 2014 +0200

    multiselect change value to "0" in AdminGenericAgent

    http://bugs.otrs.org/show_bug.cgi?id=10578