Updated to mutate access_id on visibility edit

Closes #1570 (closed)

Summary

Entity mutation on edit was not set up to save access ID meaning you couldn't edit the access IDs of posts, but the initial posting does let you set it.

Steps

1. Make a post with access set to unlisted.
2. Refresh, edit to be logged in, check it still says logged in, refresh and check again.
3. Repeat step to editing to be public.

Regression Scope

Effects the editing of activities, should be pretty fool-proof.