When submitting a job to launch, the UI will collect extra_vars from the the JT. However with a recent change to make extra_vars include comments, the UI no longer receives the JT extra vars as a JSON obj, but rather as a yaml-unparsed string. So I am changing the way we parse these JT-extra_vars from 'json' to 'yaml' since we no longer expect to recieve a json-ified extra var object.
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