ash: add testcase for bug 5304

diff --git a/shell/ash_test/ash-signals/reap1.right b/shell/ash_test/ash-signals/reap1.right
new file mode 100644
index 0000000..7326d96
--- /dev/null
+++ b/shell/ash_test/ash-signals/reap1.right
@@ -0,0 +1 @@
+Ok