sheep/recovery: fix floating point error

Once the recovery count is less than 100, sheep process will crash
because of devided by zero.

The solution is round up the recovery count first to make sure
the result is not zero.

Cc: Saeki Masaki <saeki.masaki@po.ntts.co.jp>
Signed-off-by: Ruoyu <liangry@ucweb.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>