vfs_fruit: Time Machine/FULLSYNC: add mDNS/DNS-SD advertisement

[Omri Mor]

>> Changing the adVU value, removing it, etc. all *seem* to have had no effect on the backup.
>> I just generated a completely new UUID; backup proceeded as normal.
>> Perhaps adVU helps in finding the disk if the share name changes?
>> We just don’t have documentation on *what* it does—the only reason Netatalk advertises it is because macOS Server does!
>> If it works fine without it, should we even bother?
>> 
> 
> I'd like like to re-add that all of the testing I have done is without
> an adVU value set without any ill-effects. I also did a few quick
> tests with adding it and removing it as well and from a packet capture
> point of view I could not find any identifiable differences. I am
> unsure of the exact use of it but I personally vote to leave it out as
> it the specification doesn't call it out as a hard requirement and we
> can't seem to identify a valid use for it like we can for other values
> such as the adVF=0x100 key-value pair.
> 
> -Kevin Anderson

That’s what I was thinking—implementing it complicates matters a lot, and it is
a) undocumented
b) has no identifiable use, as far as we know

Similarly, I’m not sure if we need the waMa subkey for the sys key.
That would give us:
sys=adVF=0x100
dkN=adVN=[NAME],adVF=0x82

Though I don’t think it does any harm.

Omri