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
""" Indicates whether the current request is in "debug" mode
        """
        debug = 'debug' in self.httprequest.args
        if debug and self.httprequest.args.get('debug') == 'assets':
            debug = 'assets'
        
        if not debug:
            debug = self.httprequest.environ.get('HTTP_X_DEBUG_MODE')
        if not debug and self.httprequest.referrer:
            debug = 'debug' in urls.url_parse(self.httprequest.referrer).decode_query()
        return debug
    @contextlib.contextmanager
    def registry_cr(self):
        warnings.warn('please use request.registry and request.cr directly', DeprecationWarning)
        yield (self.registry, self.cr)
    @property
    def registry(self):
        """
        The registry to the database linked to this request. Can be ``None``
        if the current request uses the ``none`` authentication.
        .. deprecated:: 8.0
            use :attr:`.env`
        """
        return odoo.registry(self.db)
    @property
    def db(self):