TriggerConfig: Workaround for issues with empty dict property handling

This is a workaround for ATR-21273 where we see a problem with handling a map<string,string> property set to an empty python dict. The value of the property ends up being a string "<no value>" in this case, and if it's set to non-empty dict, then it's and intance of GaudiConfig2.semantics._DictHelper. To ensure we get "values" from a dict-like object, a workaround is to check if it has the "values" method.

A better solution will be discussed in Jira, but we need to work around this today to ensure a working release for the Technical Run at P1.