d5e7e309 changed the `hostinfo.GetVersion` from distro and distro version
to UTS Name Release and moved distribution information under
`hostinfo.Distro*`.
`tailscale configure-host` command implementation for Synology DSM
environments relies on the old semantics of this string for matching DSM
Major version so it's been broken for a few days.
Pull in `hostinfo` and prefix match `hostinfo.DistroVersion` to match
DSM major version.
Signed-off-by: Berk D. Demir <bdd@mindcast.org>