If you don't plan to have any messages next to the subtabs, give your message div a class, and then hide it for subtabs:
var msg = $('<div class="tabmsg"></div>').appendTo($('#tt').find('div.tabs-wrap'));
msg.css({
position:'absolute',
right:0,
top:0,
height:'24px',
lineHeight:'24px',
paddingRight:'3px'
}).text('Message');
#tab-container-admin .tabmsg { display: none; }
Note: I haven't actually tried this code to see if it works, but I *think* it should.