Fix various compiler warnings

Fix various compiler warnings

This patch fixes "unused variable/unreferenced format parameter"
warnings in different places, kudos to Visual Studio compiler
for discoveing some of those.

This also also removes unneeded uninit_management_callback_multi()
wrapper.

Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <1540889615-24868-1-git-send-email-lstipakov@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg17855.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 91ba1add2f8f231a7ccf4557cdd593547e625723)