engines/libaio: reset 'wait_start' on non-EAGAIN

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/engines/libaio.c b/engines/libaio.c
index 6f62516..31c850e 100644
--- a/engines/libaio.c
+++ b/engines/libaio.c
@@ -255,9 +255,11 @@
 			ld->queued -= ret;
 			ring_inc(ld, &ld->tail, ret);
 			ret = 0;
+			wait_start = 0;
 		} else if (ret == -EINTR || !ret) {
 			if (!ret)
 				io_u_mark_submit(td, ret);
+			wait_start = 0;
 			continue;
 		} else if (ret == -EAGAIN) {
 			/*