When finding default value in Map<Object, Object> returned from script the display text is collected instead of the actual value.

 Example:

Script returns Map<Object, Object> containing versions of software the job needs to operate on:

['1.0.6': '1.0.6 (latest):selected',
 '1.0.5': 'chart:1.0.5, app:1.0.5', 
 '1.0.4': 'chart:1.0.4, app:1.0.3',
 '1.0.3': 'chart:1.0.3, app:1.0.2',
 '1.0.2': 'chart:1.0.2, app:1.0.1',
 '1.0.1': 'chart:1.0.1, app:1.0.1-SNAPSHOT', 
 '1.0.0': 'chart:1.0.0, app:1.0.0-SNAPSHOT']

Impact:
If the parameter is defined inside a pipeline and the job is run for the first time the default value is expected to be 1.0.6 but instead 1.0.6 (latest) is returned back.

Issue found here: https://github.com/jenkinsci/active-choices-plugin/blob/8eb9560476db9885bd4cd27876b2e6fc3278b01e/src/main/java/org/biouno/unochoice/AbstractScriptableParameter.java#L290

 
suggested fix: Use choices.keys()

I can prepare the pull request, no problem.