Fix memory leaks in open_tun_dco()

Fix memory leaks in open_tun_dco()

open_tun_dco_generic() already allocates the tt->actual_name string, which
shadows the allocation in the FreeBSD/Linux specific methods.

Found-By: clang with asan
Change-Id: I51f5fcfff4e5f8203fdb9aec0245cfccd17043cc
Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20230314144854.182110-2-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26411.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 021952705ba4b77a1d94bec85f6f02e6c612a37e)