fix(FormModal): ensure getButtons result has keys
fix(FormModal): ensure getButtons result has keys

Returning a list of Trans components with out `key` props was printing a
warning in the browser console. Refactored this to return a list of
buttons with key and used the Trans macro inside the button instead.

dcos/dcos-ui,dcos/dcos-ui,dcos/dcos-ui,dcos/dcos-ui,dcos/dcos-ui