This stopped working in GitLab 11.11 when we upgraded to Rails 5.1.
Rails 5 changed ActionController::Parameters to return an Object instead
of a Hash. The old behavior was deprecated in Rails 5 but finally
removed in Rails 5.1

Since the controller wasn't updated properly, the callback endpoint
quietly failed with the message, "Could not connect to FogBugz, check
your url".

To fix this, we need to call `to_h` on the `import_params` to access the
Hash. We also need to do this for the user map and permit specific keys.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/33530