Enable enable-reflector flag in avahi

[benhylau]

In the three-node mesh set up, putting this on the middle relaying node actually allows the two edge nodes to resolve each other's mDNS addresses.

While convenient, I do not plan to merge this because:

• It gives a false sense that this is how mDNS works
• Putting this on all the nodes may cause a packet storm

Build from this branch if you want to tinker with this.