fdb_rollback hangs after upgrade from v1 to v2

I am trying to verify MB-18674. The good news is that I can now see fdb file convert to v2 after compaction without crash. But I also found that fdb_rollback hangs.

1. 0x40ae0a1 github.com/couchbase/indexing/secondary/fdb._Cfunc_fdb_rollback+0x41 ??:0
2. 0x40af6b2 github.com/couchbase/indexing/secondary/fdb.(*KVStore).Rollback+0x312 /Users/jliang/Documents/eclipse/watson/watson/goproj/src/github.com/couchbase/indexing/secondary/fdb/commit.go:56
3. 0x40e1621 github.com/couchbase/indexing/secondary/indexer.(*fdbSlice).RollbackToZero+0x61 /Users/jliang/Documents/eclipse/watson/watson/goproj/src/github.com/couchbase/indexing/secondary/indexer/forestdb_slice_writer.go:938
4. 0x4178169 github.com/couchbase/indexing/secondary/indexer.(*storageMgr).handleRollback+0xb89 /Users/jliang/Documents/eclipse/watson/watson/goproj/src/github.com/couchbase/indexing/secondary/indexer/storage_manager.go:503