Fixed wrong placement of ajax timeout option

[ramonski]

Description of the issue/feature this PR addresses

Fix regression introduced in #1522 by placing the jQuery ajax timout option at the wrong place

Current behavior before PR

Traceback occurs:

Traceback (most recent call last):
  File "/Users/rbartl/.buildout/eggs/plone.jsonapi.core-0.6-py2.7.egg/plone/jsonapi/core/browser/decorators.py", line 24, in decorator
    return f(*args, **kwargs)
  File "/Users/rbartl/.buildout/eggs/plone.jsonapi.core-0.6-py2.7.egg/plone/jsonapi/core/browser/api.py", line 60, in to_json
    return self.dispatch()
  File "/Users/rbartl/.buildout/eggs/plone.jsonapi.core-0.6-py2.7.egg/plone/jsonapi/core/browser/api.py", line 54, in dispatch
    return router(self.context, self.request, path)
  File "/Users/rbartl/.buildout/eggs/plone.jsonapi.core-0.6-py2.7.egg/plone/jsonapi/core/browser/router.py", line 138, in __call__
    return self.view_functions[endpoint](context, request, **values)
  File "/Users/rbartl/develop/ridingbytes/bechem/bechem.lims/src/senaite.core/bika/lims/jsonapi/update.py", line 162, in update
    raise BadRequest("The following request fields were not used: %s.  Request aborted." % self.unused)
BadRequest: The following request fields were not used: ['timeout'].  Request aborted.

Desired behavior after PR is merged

No traceback occurs

--
I confirm I have tested this PR thoroughly and coded it according to PEP8
and Plone's Python styleguide standards.