check if value is actually jinja before adding as template

[guzzijones]

check if the value is actually jinja and not a string like {"someurl": "http://test?value={{test"}

[arm4b]

Please include a Changelog for this fix.

Did you get an exception somewhere, how the error looked like?
A more specific example with steps to reproduce and log in the first message would help for the future history and others hitting the same issue.

[guzzijones]

If your parameter value has a {{ or {% in it and it is not closed you will see the following exception in the st2workflowengine.log file: TemplateSyntaxError: expected token 'end of print statement', got 'string'

[arm4b]

Thanks for Changelog and additional context! 👍