FTAM — Transfer operation protocol negotiation unspecified

In Section 3.2 File Transfer Session, the transfer operation is
described requires the source FileTransferSession and Target
FileTransferSession to negotiate the transfer protocol by inspecting
each other's protocols_supported attribute.

This is problematic if either FileTransferSession supports more than
one protocol as the protocol negotiation is not specified.

For example take two FileTransferSessions that list their supported
protocols in their preferred order:

FileTransferSession (A) FileTransferSession (B)
---------------------- -----------------------
supported_protocols: supported_protocols:
1. "TCP/IP:xxx.xxx.xx.xx:yyy" 1. "Other:adafadfasdfd"
2. "Other:adfadfasdfadfdf" 2. "TCP/IP:xxx.xxx.xx.xx:yyy"

Even though they both support the same protocols, if these two
FileTransferSessions attempt a transfer using the Code sample in
Section 4.5.2, A will select TCP/IP, B will select "Other" and the
transfer will never happen.

Action Requested: specify transfer protocol selection method.

see above