Eliminate check_incoming_control_channel wrapper function

Eliminate check_incoming_control_channel wrapper function

Move the check that calls this function into the calling function.
Also eliminate the if (len) check in the
check_incoming_control_channel_dowork function as it is only called
if len is > 0 anyway and replace it with a ASSERT.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20200810143707.5834-11-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg20680.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>