avahi-discover failed to display selected service details with UnicodeDecodeError

[林博仁(Buo-ren, Lin)]

## Bug reproduce instruction
(As this is a Unicode decode issue it might not be reproducible in all network environments)

1. Launch avahi-discover
2. Select certain service

## Expected behavior
The service details properly rendered on the bottom pane

## Current behavior
The service details remain "No service currently selected" with the following error traceback:

```
Found service 'Buo-ren-TS453A' of type '_qdiscover._tcp' in domain 'local' on 2.0.
Service data for service 'Buo-ren-TS453A' of type '_qdiscover._tcp' in domain 'local' on 2.0:
        Host Buo-ren-TS453A.local (192.168.1.10), port 8080, TXT data: ['accessType=http,accessPort=8080,model=TS-X53II,displayModel=TS-453A,fwVer=4.3.4,fwBuildNum=20180830,serialNum=Q169I13903,myCloudNASName=LinBuoRenNAS,myCloudNASDomain=myqnapcloud.com,webAdmPort=0,webAdmSslPort=0,webPort=0,webSslPort=0']
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/dbus/connection.py", line 604, in msg_reply_handler
    reply_handler(*message.get_args_list(**get_args_opts))
  File "/usr/bin/avahi-discover", line 113, in service_resolved
    self.update_label(interface, protocol, name, stype, domain, host, aprotocol, address, port, avahi.txt_array_to_string_array(txt))
  File "/usr/bin/avahi-discover", line 246, in update_label
    infos = infos % (stype, name, domain, self.siocgifname(interface), self.protoname(protocol), host, address, port, txts.strip())
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe6 in position 6: ordinal not in range(128)
```

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Anders Fromell (konsultnisse)]

I have seen this in about 20 Lubuntu/Ubuntu 16.04 installations dist upgraded to 18.04
Also it works in some others..

I did NOT see this prior to avahi-daemon version 0.70

No idea what breaks it, however avahi-browse seams to work.
Can it be something related with the support for "binary records" starting in 0.7x

In a fresh 18.04 installation MDNS in general seams to be broken/disabled

[ftoledo (ftoledo)]

same error on debian with avahi-disvover 0.7-4+deb10u1