zdtm: exit with the zero code if everything is ok

Cc: Yicheng Qin <yichengq@google.com>
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm.sh

@@ -733,4 +733,4 @@ else
 fi
 
 [ -n "$TMP_TREE" ] && rm -rf $TMP_TREE
-[ -n "$ZDTM_FAILED" ] && exit 1
+[ -n "$ZDTM_FAILED" ] && exit 1 || exit 0