[MEDIUM] stream_interface: add and use ->update function to resync

We used to call stream_sock_data_finish() directly at the end of
a session update, but if we want to support non-socket interfaces,
we need to have this function configurable. Now we access it via
->update().
diff --git a/src/proto_uxst.c b/src/proto_uxst.c
index c811f64..60efb6d 100644
--- a/src/proto_uxst.c
+++ b/src/proto_uxst.c
@@ -445,11 +445,12 @@
 		s->si[0].err_type = SI_ET_NONE;
 		s->si[0].err_loc = NULL;
 		s->si[0].owner = t;
-		s->si[0].connect = NULL;
+		s->si[0].update = stream_sock_data_finish;
 		s->si[0].shutr = stream_sock_shutr;
 		s->si[0].shutw = stream_sock_shutw;
 		s->si[0].chk_rcv = stream_sock_chk_rcv;
 		s->si[0].chk_snd = stream_sock_chk_snd;
+		s->si[0].connect = NULL;
 		s->si[0].fd = cfd;
 		s->si[0].flags = SI_FL_NONE;
 		s->si[0].exp = TICK_ETERNITY;
@@ -458,11 +459,12 @@
 		s->si[1].err_type = SI_ET_NONE;
 		s->si[1].err_loc = NULL;
 		s->si[1].owner = t;
-		s->si[1].connect = NULL;
+		s->si[1].update = stream_sock_data_finish;
 		s->si[1].shutr = stream_sock_shutr;
 		s->si[1].shutw = stream_sock_shutw;
 		s->si[1].chk_rcv = stream_sock_chk_rcv;
 		s->si[1].chk_snd = stream_sock_chk_snd;
+		s->si[1].connect = NULL;
 		s->si[1].exp = TICK_ETERNITY;
 		s->si[1].fd = -1; /* just to help with debugging */
 		s->si[1].flags = SI_FL_NONE;