Update bugzilla.py

Trivial fix for dictionary key error when updating the bug status.

Traceback (most recent call last):
  File "/usr/local/bin/bugzilla", line 5, in <module>
    pkg_resources.run_script('bugzillatools==0.5.3.1', 'bugzilla')
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 528, in run_script
    self.require(requires)[0].run_script(script_name, ns)
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 1394, in run_script
    execfile(script_filename, namespace, namespace)
  File "/usr/local/lib/python2.7/dist-packages/bugzillatools-0.5.3.1-py2.7.egg/EGG-INFO/scripts/bugzilla", line 83, in <module>
    args.command(args, parser, commands, aliases, ui)()
  File "/usr/local/lib/python2.7/dist-packages/bugzillatools-0.5.3.1-py2.7.egg/bzlib/command.py", line 728, in __call__
    values = self.bz.get_field_values('bug_status')
  File "/usr/local/lib/python2.7/dist-packages/bugzillatools-0.5.3.1-py2.7.egg/bzlib/bugzilla.py", line 166, in get_field_values
    values = filter(lambda x: x['name'], values)
  File "/usr/local/lib/python2.7/dist-packages/bugzillatools-0.5.3.1-py2.7.egg/bzlib/bugzilla.py", line 166, in <lambda>
    values = filter(lambda x: x['name'], values)
KeyError: 'name'