Suggest strategy for enumerating remote files to be downloaded using SFTPFileTransfer

At this point in SSHJ, there is special logic to account for SFTP servers that do not supply file type information.

https://github.com/hierynomus/sshj/blob/master/src/main/java/net/schmizz/sshj/sftp/SFTPFileTransfer.java#L124-L127

That is, if the file type is UNKNOWN, the file is downloaded as if the type were REGULAR.

Seeking insight as to whether remote file enumeration logic should similarly ignore `remote.getAttributes().getType() == UNKNOWN`.