when Close or Recovery Indexer, it's need to reset the Offset

[scottzzq]

when Close or Recovery Indexer, it's need to reset the Index.Offset

[Terry-Mao]

Indexer&Block Close&Open used for Flush inner buffer and close inner goroutine handler, so all struct status MUST keep.

sth like:

NewIndexer
NewBlock

try to recovery block & index, then start all handler goroutine.

Close called by a empty Volume , free Volume ,they wait for add a new volume.

so offset may has it's status.

[Terry-Mao]

NewIndexer -> Recovery -> Close -> [wait for new a volume] -> Open

After Recovery, Offset must keep for Open

[scottzzq]

When running the index_test.go, the process is:
NewIndexer
Add
Close
Recovery
Add
Because the Recocery process will add the Offset again, the Offset will be wrong.
So, I think, in the Recovery code, Offset should be reset 0.

[Terry-Mao]

okay, i'll fix the go test, it's confused