vty: Fix writing the logging of category

Fix copy and paste issue introduced by Holger in
2d6ad13d8daf860595e6d4025861e122ce574871.
diff --git a/src/vty/logging_vty.c b/src/vty/logging_vty.c
index 40daba1..a23c1a7 100644
--- a/src/vty/logging_vty.c
+++ b/src/vty/logging_vty.c
@@ -660,7 +660,7 @@
 	vty_out(vty, "  logging color %u%s", tgt->use_color ? 1 : 0,
 		VTY_NEWLINE);
 	vty_out(vty, "  logging print category %d%s",
-		tgt->print_ext_timestamp ? 1 : 0, VTY_NEWLINE);
+		tgt->print_category ? 1 : 0, VTY_NEWLINE);
 	if (tgt->print_ext_timestamp)
 		vty_out(vty, "  logging print extended-timestamp 1%s", VTY_NEWLINE);
 	else