workaround for bad output format dpkg-query command

fixes the following error trace:

  File "/usr/lib/pymodules/python2.7/salt/state.py", line 1258, in call
    *cdata['args'], **cdata['kwargs'])
  File "/usr/lib/pymodules/python2.7/salt/states/pkg.py", line 421, in installed
    fromrepo=fromrepo, **kwargs)
  File "/usr/lib/pymodules/python2.7/salt/states/pkg.py", line 108, in _find_install_targets
    cur_pkgs = __salt__['pkg.list_pkgs'](versions_as_list=True)
  File "/usr/lib/pymodules/python2.7/salt/modules/apt.py", line 609, in list_pkgs
    [cols[x] for x in (0, 2, 3, 4, 5)]
IndexError: list index out of range