localechooser in ubiquity will pick lzh_TW instead of zh_TW when timezone set to Taipei

Steps to reproduce:
1. Install Ubuntu, use English as default language but manually set the timezone to Taipei
2. Boot to desktop, run command `locale`

Expected Result:
* You should only see "en_US.UTF-8" and "zh_TW" in the output

Actual Result:
* You will see "lzh_TW" instead.

Impact:
This will cause error when running commands like apport, which will call the locale.py in Python

Traceback (most recent call last):
  File "/usr/share/apport/apport-gtk", line 598, in <module>
    app.run_argv()
  File "/usr/lib/python3/dist-packages/apport/ui.py", line 694, in run_argv
    return self.run_crashes()
  File "/usr/lib/python3/dist-packages/apport/ui.py", line 245, in run_crashes
    logind_session[1] > self.report.get_timestamp():
  File "/usr/lib/python3/dist-packages/apport/report.py", line 1684, in get_timestamp
    orig_ctime = locale.getlocale(locale.LC_TIME)
  File "/usr/lib/python3.6/locale.py", line 581, in getlocale
    return _parse_localename(localename)
  File "/usr/lib/python3.6/locale.py", line 490, in _parse_localename
    raise ValueError('unknown locale: %s' % localename)
ValueError: unknown locale: lzh_TW

(Bug opened for Python https://bugs.python.org/issue32781)