Previously, any change to endpoints or hostinfo (or hostinfo's
netinfo) would result in the long-running map request HTTP stream
being torn down and restarted, losing all compression context along
with it.
This change makes us instead send a lite map request (OmitPeers: true,
Stream: false) that doesn't subscribe to anything, and then the
coordination server knows to not close other streams for that node
when it recives a lite request.
Fixestailscale/corp#797
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>