We're seeing ADT timeouts with snapd due to a regression in
virtio_net network performance under some unknown circumstances.
Bisection identified 680557cf79f8 ("virtio_net: rework mergeable
buffer handling") as the commit introducing the regression. This
patch is effectively a revert of that patch and two other follow-
up patches:
e377fcc8486d virtio_net: reduce alignment for buffers
56da5fd04e3d virtio_net: tidy a couple debug statements
With these reverts the data rate when downloading snaps returns
to normal.
This should be dropped once a proper fix is available upstream
