Fix an issue where excluded recipients are not respected

Summary: I broke this in D3778. We modify $parameters and then ignore it in favor of $params for the rest of the method. Unit tests work great since they're one level below this.

Test Plan: Verified "Send email about my own actions" behaved correctly.

Reviewers: vrana, btrahan

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D3796