look for HieroTankWrite MetaData nodes and convert to WriteTank nodes
Ticket #22399 - Changed from Hiero node to more generic placeholder.  Only pass
through the profile name and channel name.
Ticket #22399 - Remove the onScriptLoad callback on app destroy
Merge pull request #1 from shotgunsoftware/22399_published_files

#22399 look for ShotgunWriteNodePlaceholder MetaData nodes and convert to WriteTank nodes