Cannot append stats

[stephenrblair2]

Describe the bug
If you set the Stats Mode to Append, it doesn't work.

To Reproduce
Steps to reproduce the behavior:

1. In the Arnold Render Settings LOP, on the Diagnostics tab, set Stats Mode to Append.
2. Render a bunch of frames, or do a bunch of IPR renders.
3. Stats are not appended.

husk and kick both have the problem.

Used Software Versions

• Arnold: 7.4.1

Additional context

stats mode is set twice:

https://github.com/Autodesk/arnold-usd/blob/d9c32fcb220c015b42721f9a728bfd4c80929249/libs/render_delegate/render_delegate.cpp#L711C11-L712C44

[autodesk-oss-arnold-bot]

Issue synced internally to ARNOLD-16282