Small fixes for file transfer

fileTransfer/fileMessage_test.go

fileTransfer/manager.go

fileTransfer/manager_test.go

fileTransfer/oldTransferRecovery.go

fileTransfer/oldTransferRecovery_test.go

fileTransfer/receive_test.go

fileTransfer/send.go

fileTransfer/send_test.go

fileTransfer/utils_test.go

storage/fileTransfer/partStore_test.go

storage/fileTransfer/receiveFileTransfers.go

storage/fileTransfer/receiveFileTransfers_test.go

storage/fileTransfer/receiveTransfer.go

storage/fileTransfer/receiveTransfer_test.go

storage/fileTransfer/receivedCallbackTracker.go

storage/fileTransfer/receivedCallbackTracker_test.go

storage/fileTransfer/receivedPartTracker.go

storage/fileTransfer/receivedPartTracker_test.go

storage/fileTransfer/sentCallbackTracker.go

storage/fileTransfer/sentCallbackTracker_test.go