Ensure controlled vocabulary terms are searchable

[bess]

When I add a metadata field that is marked as
controlled vocabulary, I expect it to be searchable. Instead, adding a new controlled vocabulary term initially seems not to produce a searchable field. In an experiment, if the field was marked as free text and then turned back to controlled vocabulary, the search for that field started working.

• Write a unit test so we can test this in a repeatable way
• Ensure that newly added controlled vocabulary terms are searchable