connection: Fix sendmsg() on FreeBSD
connection: Fix sendmsg() on FreeBSD

It expects ((msg_controllen == 0) == (msg_control == NULL)), and returns
EINVAL otherwise. It can't hurt to be tidy about things on other platforms
either though.

See: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=99356#c5

Signed-off-by: Philip Withnall <philip at tecnocode.co.uk>
Signed-off-by: Karsten Otto <ottoka at posteo.de>
Reviewed-by: Pekka Paalanen <0f6ae7001e34c37b02fb2c1c2573ddf8f442136a@collabora.co.uk>

abooij/wayland,sir-murray/wayland,mchalupa/wayland,bitfactor/wayland,tulcod/wayland,bitfactor/wayland,eyolfson/wayland,mchalupa/wayland,bitfactor/wayland,sir-murray/wayland,sir-murray/wayland,abooij/wayland,mchalupa/wayland,eyolfson/wayland,tulcod/wayland,eyolfson/wayland,abooij/wayland,tulcod/wayland