zookeeper: explecitly ask users to wait to restart sheep

Not every users is zookeeper guru, so we should make log as friendly as possible

Reviewed-by: Robin Dong <sanbai@taobao.com>
[ add back whitespace for tests/func/{081,082} output in passing to save an
  patch along with this patch - Yuan ]
Signed-off-by: Liu Yuan <namei.unix@gmail.com>