MFC r368394:
When dropping packets (RRQ or WRQ) for debugging, report the send
operation as successful. Reporting a failure stops the transfer
instead of using timeouts.

MFC r368521:
Fix the TFTP client when performing a RRQ for files smaller than 512 bytes
and the server not sending an OACK:

• Close the file.
• Report the correct the number of received blocks.

MFC r368647:
Improve the counting of blocks used to transfer a file from the
server to the client in case of not using an OACK: Don't miss
the first block in case of it is not also the last one.

MFC r368657:
When receiving a file having a length, which is a mulitple of the blocksize,
close the file once it is received.