hush: fix exitcodes of killed processes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/shell/hush_test/hush-misc/sig_exitcode.right b/shell/hush_test/hush-misc/sig_exitcode.right
new file mode 100644
index 0000000..d5f000a
--- /dev/null
+++ b/shell/hush_test/hush-misc/sig_exitcode.right
@@ -0,0 +1,5 @@
+KILL
+137:137
+KILL
+0:0
+Done