Noticed when testing FUS on tailscale-on-macOS, that routing would break
completely when switching between profiles. However, it would start working
again when going back to the original profile tailscaled started with.
Turns out that if we change the addrs on the interface we need to remove and readd
all the routes.
Updates #713
Signed-off-by: Maisem Ali <maisem@tailscale.com>