Fix Render problem when the Multiline TextBox, is in a UpdatePanel or an...

...other container

In the next example you can See, the problem the TextBox appends to begin a tab ('\t') character

<%@ Page Language="C#" AutoEventWireup="true" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:ScriptManager runat="server" ID="S"></asp:ScriptManager>
        <asp:UpdatePanel runat="server" ID="U" Visible="true" UpdateMode="Conditional">
        <ContentTemplate>
            <asp:TextBox runat="server" ID="T" TextMode="MultiLine" Text="Text"></asp:TextBox>
        </ContentTemplate>
        </asp:UpdatePanel>
        <asp:TextBox runat="server" ID="E" TextMode="MultiLine" Text="Text"></asp:TextBox>
    </div>
    </form>
</body>
</html>