Revert "Revert "tcp: ensure to use the most recently sent skb when filling the rate sample""

This reverts commit 5deab346.

It was originally reverted as it broke the abi but can now be safely
brought back.

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I1a084a80d2f0c669874468ad897c7d104016f1c6