use M_ERRNO instead of explicitly printing errno

use M_ERRNO instead of explicitly printing errno

the msg() function will print the errno for us when
provided with the M_ERRNO flag.

Therefore, don't bother printing errno explicitly and always
pass M_ERRNO to msg().

Signed-off-by: Antonio Quartulli <antonio@openvpn.net>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <20170713080527.13299-1-a@unstable.cc>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg15056.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 56b396dcbc34ffd3cddeb2e65ae55c40eae51831)