NAKACK2 / UNICAST2: last message sent to self may not get delivered

When A sends a message M that's received by A (M is either a multicast, or a unicast to A), and the message is dropped below NAKACK2 / UNICAST2, then A might receive M, but not deliver it if M is the last message sent.

Scenario (for NAKACK2, but similar to UNICAST2):

• A's table is: HD=9, HR=9
• A sends M10
• NAKACK2 adds M10: HD=9, HR=10 (highest-delivered is still 9, as we haven't removed M10 yet)
• The transport drops M10
• A sends no further messages
• STABLE will make sure that A's HR is 10, but since no message was received, we won't remove any messages from A's table !

--> The result is that although A received M10, it won't deliver M10 (until another message is received) !

SOLUTION:

• Maybe we can use the retransmit task to see if there are any unremoved messages in a table and - if so - remove them and pass them up the stack to the application.