VTEmailTask using incorrect signature.

Basically, when the Workflow task generates the email, it always adds the signature of the assigned user, not the person who edited the thing that triggered the workflow or, the user that is configured in the from field of the workflow task. See this thread on the mailing list for more info.

http://lists.vtigercrm.com/pipermail/vtigercrm-developers/2018-May/037487.html

Issue is caused here:
http://code.vtiger.com/vtiger/vtigercrm/blob/master/modules/com_vtiger_workflow/tasks/VTEmailTask.inc#L341

because the "$fromUserId" is actually not always correct. It is defined here to be the Assigned To, and NOT the real "From" user: http://code.vtiger.com/vtiger/vtigercrm/blob/master/modules/com_vtiger_workflow/tasks/VTEmailTask.inc#L213