Instead of pulling packages from pkgs.tailscale.com, we should use the
tailscale binaries that are local to this git commit. This exposes a bit
of the integration testing stack in order to copy the binaries
correctly.
This commit also bumps our version of github.com/pkg/sftp to the latest
commit.
If you run into trouble with yaml, be sure to check out the
commented-out alpine linux image complete with instructions on how to
use it.
Updates #1988
Signed-off-by: Christine Dodrill <xe@tailscale.com>
