Fix zones for numjobs=x, where x > 1

In the options fixup, we auto-set open_files to 1 if it hasn't been set.
So any duplicated jobs will clear the zone. Fixup the check to properly
check for > 1 open files.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/init.c b/init.c
index 60ba299..e8f3a9b 100644
--- a/init.c
+++ b/init.c
@@ -408,7 +408,7 @@
 	/*
 	 * only really works with 1 file
 	 */
-	if (o->zone_size && o->open_files == 1)
+	if (o->zone_size && o->open_files > 1)
 		o->zone_size = 0;
 
 	/*