ipaccess: allow tcp keepalive for ipa clients

This allows using the e1_line x keepalive y z setting for clients like
osmo-bts.

Change-Id: Iadf22934ca6d3c44adac5573709ba53e75fa07da
diff --git a/src/input/ipaccess.c b/src/input/ipaccess.c
index 136aa79..d0fa023 100644
--- a/src/input/ipaccess.c
+++ b/src/input/ipaccess.c
@@ -667,8 +667,10 @@
 {
 	struct e1inp_line *line = link->line;
 
-	if (up)
-		return;
+        if (up) {
+                update_fd_settings(line, link->ofd->fd);
+                return;
+        }
 
 	if (line->ops->sign_link_down)
 		line->ops->sign_link_down(line);