Comment # 6 on bug 1177039 from Franck Bui

The only workaround I can think of is something like:

--------
%pre <new-name>
if <package_is_being_installed>; then
    rpm -q <old-name> && touch /run/<new-name>/package-is-renamed
fi


%post <new-name>
if ! test -e /run/<new-name>/package-is-renamed; then
    # Assign 2 to $1 and pretend that a package update is on going.
    set 2
fi
%service_add_post sshd.service
rm -f /run/<new-name>/package-is-renamed
---------

and yes that's pretty hackish.