The SFTP client does not work with read-once servers

Some SFTP servers only allow a file to be read once. However, when the SFTP client downloads a file, it first sends a Stat command to the server to retrieve the file's information. That command causes conflicts with the server's one time read policy, which makes the transfer fail. This can be fixed by adding the UseConcurrentReads(false) when opening the session.

We might need to add an option in the protoConfig to enable that behavior, as it might have an impact on performance.