Bugfix: The bootstrap script is overwriting existing multi-valued settings.

Bugfix: The bootstrap script is overwriting existing multi-valued settings.

This is a back port of commit 74f0689d3f7dc91a65b6069b9052580cab59601e.

This happens when there are multiple modes specifying the same value.
The multi-valued settings must have the value appended and not overwritten or removed.

Specifically, the setting is designated as not populated when a mode specifies a setting and then is followed by another mode that does not specify this setting.

Resolve this by adding checks if the setting is already designated as specified.
If the settings is not specified, then and only then declare it as unspecified.