Impacted versions: 8-11

## Current behavior:

If during an XMLRPC call you try to get anything from `http.request`, you'd get a `RuntimeError` such as this one:

```
Traceback (most recent call last):
  File "/opt/odoo/custom/src/odoo/odoo/service/wsgi_server.py", line 56, in xmlrpc_return
    result = odoo.http.dispatch_rpc(service, method, params)
  File "/opt/odoo/custom/src/odoo/odoo/http.py", line 118, in dispatch_rpc
    result = dispatch(method, params)
  File "/opt/odoo/custom/src/odoo/odoo/service/common.py", line 57, in dispatch
    return g[exp_method_name](*params)
  [...]
  File "/usr/local/lib/python2.7/dist-packages/werkzeug/local.py", line 343, in __getattr__
    return getattr(self._get_current_object(), name)
  File "/usr/local/lib/python2.7/dist-packages/werkzeug/local.py", line 302, in _get_current_object
    return self.__local()
  File "/usr/local/lib/python2.7/dist-packages/werkzeug/local.py", line 135, in _lookup
    raise RuntimeError(\'object unbound\')
RuntimeError: object unbound
```

This renders imposible in practice to fix issues such as https://github.com/OCA/server-tools/issues/1125 or to implement https://github.com/odoo/odoo/pull/22212#issuecomment-380425764.

## Expected behavior:

XML-RPC calls should have request, since after all they belong to one. Otherwise, at least there should be an alternate way to access the request parameters.

Fix for v12: https://github.com/odoo/odoo/pull/24187

@Tecnativa
odoo/http.py
""" Handler for the ``http`` request type.
    matched routing parameters, query string parameters, form_ parameters
    and files are passed to the handler method as keyword arguments.
    In case of name conflict, routing parameters have priority.
    The handler method's result can be:
    * a falsy value, in which case the HTTP response will be an
      `HTTP 204`_ (No Content)
    * a werkzeug Response object, which is returned as-is
    * a ``str`` or ``unicode``, will be wrapped in a Response object and
      interpreted as HTML
    .. _form: http://www.w3.org/TR/html401/interact/forms.html#h-17.13.4.2
    .. _HTTP 204: http://tools.ietf.org/html/rfc7231#section-6.3.5
    """
    _request_type = "http"
    def __init__(self, *args):