[SRU] Mugshot fails to expand user details

[Impact]
For some users, Mugshot may fail to start because it was unable to expand
user details from /etc/passwd. This was fixed in the following revision,
in Mugshot 0.2.4:
https://bazaar.launchpad.net/~mugshot-dev/mugshot/trunk/revision/122

This fix avoids the following fatal startup error.

Traceback (most recent call last):
  File "/usr/bin/mugshot", line 35, in <module>
    mugshot.main()
  File "/usr/lib/python3/dist-packages/mugshot/__init__.py", line 45, in main
    window = MugshotWindow.MugshotWindow()
  File "/usr/lib/python3/dist-packages/mugshot_lib/Window.py", line 50, in __new__
    new_object.finish_initializing(builder)
  File "/usr/lib/python3/dist-packages/mugshot/MugshotWindow.py", line 217, in finish_initializing
    self.init_user_details()
  File "/usr/lib/python3/dist-packages/mugshot/MugshotWindow.py", line 247, in init_user_details
    name, office, office_phone, home_phone = details.split(',', 3)
ValueError: need more than 1 value to unpack

[Test Case]
1. Set your account name to "A".
2. Clear any other contact details from /etc/passwd (using chfn)
3. Start Mugshot.

[Expected Results]
Mugshot should start successfully.

[Regression Potential]
None. This release pads the account details so that this scenario is no longer possible.