Revert "sheep/recovery: reduce network overhead of preparing object list"

This reverts commit f56aceee959baa1127de5e0babbacb9e8971ceaa.

Quote from Ruoyu

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Although the probability is rather low, the patch will cause the vm
file system crashed.

Suppose that there are 3 nodes in a cluster: A, B and C. A is fast and
B is slow. Now C is left accidently. Let us focus on node B, if
GET_OBJ_LIST request of A is received prior to the zookeeper
EVENT_LEAVE message, B will return object list on the old epoch to A.
However, what node A want to get is the object list on the new epoch.
Therefore, some objects cannot be recovered. That is the problem.

To simplify the scenario, I think it is better to use the old
algorithm, getting all object list first, and then, checking which
objects are belong to the node itself.