BUG/MEDIUM: stream_interface: restore get_src/get_dst

BUG/MEDIUM: stream_interface: restore get_src/get_dst

Commit e164e7a removed get_src/get_dst setting in the stream interfaces but
forgot to set it in proto_tcp. Get the feature back because we need it for
logging, transparent mode, ACLs etc... We now rely on the stream interface
direction to know what syscall to use.

One benefit of doing it this way is that we don't use getsockopt() anymore
on outgoing stream interfaces nor on UNIX sockets.