MINOR: connection: always initialize conn->objt_type to OBJ_TYPE_CONN

We do this everywhere we prepare a connection so that we can safely
switch to objt_conn() next.
diff --git a/src/proto_http.c b/src/proto_http.c
index 2234b91..dc3c9a9 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -4283,6 +4283,7 @@
 	s->target = NULL;
 
 	s->req->cons->state     = s->req->cons->prev_state = SI_ST_INI;
+	s->req->cons->conn->obj_type = OBJ_TYPE_CONN;
 	s->req->cons->conn->t.sock.fd = -1; /* just to help with debugging */
 	s->req->cons->conn->flags = CO_FL_NONE;
 	s->req->cons->conn->err_code = CO_ER_NONE;