[libvirt] [PATCH] Fiz macvtap test on Debian

Hi, Debian's (and therefore likely the derivatives') kernel headers are lacking the typdef for sa_family_t in linux/socket.h so the compilation of the macvtap check fails. Additionally including sockaddr.h fixes this and doesn't hurt the other cases where there's also a typedef in socket.h since these two must be identical. Cheers, -- Guido