hush: fix "while false; ..." exitcode; add testsuites

diff --git a/shell/hush_test/hush-misc/while1.right b/shell/hush_test/hush-misc/while1.right
new file mode 100644
index 0000000..7c4d7be
--- /dev/null
+++ b/shell/hush_test/hush-misc/while1.right
@@ -0,0 +1 @@
+OK:0