Update email notification logic to honor should_send_own_update flag
Fixes: 3684, 3681
If a user was explicitly listed in a review request along with also being a member of a group assigned to a request, the should_send_own_update setting in the users profile would not be honored because the check was happening before we added explicit users to the to_field list. This also fixes the issue where we were trying to remove email address that might not actually exist (a blank review request).

Had a user create a review request that lists me as an explicit reviewer along with a group that I'm also a member of; commented on the issue and I never recieved an email notification.