fix: remove quotation of flags in systemd config file

Remove the quotation around the collector option flags and values
in the node_exporter role systemd unit config file template so that
regex values get parsed correctly.

Refs: #68
Signed-off-by: Andrew Kingston <andrew.kingston@framestore.com>

roles/node_exporter/templates/node_exporter.service.j2

@@ -16,7 +16,7 @@ ExecStart={{ node_exporter_binary_install_dir }}/node_exporter \
 {%     set name, options = (collector.items()|list)[0] -%}
     --collector.{{ name }} \
 {%     for k,v in options|dictsort %}
-    {{ ( '--collector.' + name + '.' + k + '=' + v  ) | quote }} \
+    --collector.{{ name }}.{{ k }}={{ v }} \
 {%     endfor -%}
 {%   endif -%}
 {% endfor -%}