Workflow approver shown as message boards message author

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 7.4.1 CE GA2, 7.4.X
• Fix Version/s: 7.4.2 CE GA3, Master
• Component/s: Message Boards
• Labels: None
• Story Points: 1
• Fix Priority: 4
• Sprint: LIMA |QA Sprint 11
• Git Pull Request: https://github.com/liferay-lima/liferay-portal/pull/2082

Steps to reproduce:

1. Enable Simple Approval Workflow in MB
2. Create a MB message with user A.
3. Assert MB message author name is A's.
4. Approve MB message with user B 

Expected behavior: Subscribers are notified about MB message with author = A

Current behavior: Subscribers are notified about MB message with author = B

This issue also affects Questions, which is based on MB.

Technical aspects: 

Workflow reviewer's user is being passed to Message Board notifications upon approval.  This leads to notification emails stating the workflow reviewer is the original poster of the message instead of the actual poster. 

It should instead use the user from the original message instead of the currently logged in user for sending the notification.

The user used during notifications is defined here.