Merge "[FAB-13000] Release resources in token transactor"

token/ledger/ledger.go

token/ledger/mock/ledger_reader.go

token/ledger/mock/ledger_writer.go

token/server/mock/transactor.go

token/server/prover.go

token/server/tms.go

token/tms/plain/ledger.go

token/tms/plain/transactor.go