hnbgw_vty.c: Fix "-Werror=format-security" failure in vty_out()

We have to use a format string, we cannot directly print "name".

Fixes a build error on our OBS builds:
hnbgw_vty.c:156:5: error: format not a string literal and no format arguments [-Werror=format-security]
which was introduced in Change-Id I3c937306a011715e163a40bc8ef8ec7e8d4e5d08
about one week ago.

Change-Id: I042989c2b7b379284b2ee5fea3bd8f8ce406b09e
diff --git a/src/hnbgw_vty.c b/src/hnbgw_vty.c
index 2c47bba..859cd31 100644
--- a/src/hnbgw_vty.c
+++ b/src/hnbgw_vty.c
@@ -153,7 +153,7 @@
 	    vty_out(vty, "(no addr)");
 	    return;
 	}
-	vty_out(vty, name);
+	vty_out(vty, "%s", name);
 	talloc_free(name);
 }