1) Don't call security_unix_may_send() hook during sendmsg() for 
SOCK_SEQPACKET, and ensure that sendmsg() can only be called on a 
connected socket so as not to bypass the security_unix_stream_connect() 
hook.

2) Return -EINVAL if sendto() is called on SOCK_SEQPACKET with an address 
supplied.
Signed-off-by: James Morris <jmorris@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>