Remove multiple bickets might clear next group

When remove multiple bucket, the group handler doesn't check keys in next group after it remove key chains.

Originally this will not be happened because we can only remove one bucket at same time, the group handler will check if the bucket is the last bucket in the group.

However, after we finish issue CORD-555 and CORD-966, we support add/remove multiple bucket at same time. If we remove multiple at same time, it will bypass the check and cleanup the next group.