It might as well have been spewing out gibberish. This adds
a nicer output format for us to be able to read and identify
whats going on.
Sample output
```
natV4Config{nativeAddr: 100.83.114.95, listenAddrs: [10.32.80.33], dstMasqAddrs: [10.32.80.33: 407 peers]}
```
Fixestailscale/corp#14650
Signed-off-by: Maisem Ali <maisem@tailscale.com>