fixed object dump in collectd.python

[Logioniz]

Wrong dump python object with quotes (need double quotes)

Actual behavior

Pillar:

collectd:
  plugins:
    python:
      modules:
        elasticsearch:
          variables:
            AdditionalMetrics: [""]

Generated file:

    <Module "elasticsearch">
        AdditionalMetrics ['']
        ...
    </Module>

Error

collectd[1581]: configfile: Cannot read file `/etc/collectd/plugins/python.conf'.
systemd[1]: Unit collectd.service entered failed state.
collectd[1581]: ['']

Expected behavior

    <Module "elasticsearch">
        AdditionalMetrics [""]
        ...
    </Module>