selinux: Assign proper class to PF_UNIX/SOCK_RAW sockets

For PF_UNIX, SOCK_RAW is synonymous with SOCK_DGRAM (cf.
net/unix/af_unix.c). This is a tad obscure, but libpcap uses it.

Signed-off-by: Luis Ressel <aranea@aixah.de>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>