Fixes for ApprovedRevs integration

Changes:

1. Add two more parameters to onDrawioGetFile (approvalStatus and approvedImage)
2. Remove unused $img_url_ts from onDrawioGetFile
3. Change the visibility of the placeholder with respect to approval status

Change-Id: I5d98a45b6c5253fc49ea00c4ec89c77a6f0f0a52