REORG: Initialize the conn-stream by hand in cs_init()

The function cs_init() is only called by cs_new(). The conn-stream
initialization will be reviewed. It is easier to do it in cs_new() instead
of using a dedicated function. cs_new() is pretty simple, there is no reason
to split the code in this case.
diff --git a/src/conn_stream.c b/src/conn_stream.c
index 01541a5..53b2992 100644
--- a/src/conn_stream.c
+++ b/src/conn_stream.c
@@ -29,7 +29,15 @@
 	cs = pool_alloc(pool_head_connstream);
 	if (unlikely(!cs))
 		return NULL;
-	cs_init(cs);
+
+	cs->obj_type = OBJ_TYPE_CS;
+	cs->flags = CS_FL_NONE;
+	cs->end = NULL;
+	cs->app = NULL;
+	cs->ctx = NULL;
+	cs->si = NULL;
+	cs->data_cb = NULL;
+
 	return cs;
 }