3.2.3rc1: workaround for making ColumnMap-callback functional again

The code in Elements/Ticket/RT__Ticket/ColumnMap moved from the <%INIT> to
a <%ONCE> section (i guess for performance reason).

The drawback of this is, that the callback “ColumnMap” at the end of the
code is no longer called making own additions unfunctional. As a workaround
I moved the callback code to the <%INIT> section. There might be a better
solution which I did not find.