Primvars not being passed to Arnold

[cpichard]

Describe the bug
Since version 6.2.30 some of the primvars like primvars:Pref are not correctly translated to arnold, which causes issues with shading/AOVS etc.

To Reproduce
Steps to reproduce the behavior:

1. open the attached usd file with usdview with arnold-usd 7.2.3 and 7.2.2. (make sure Enable Materials is on)
   htoa_primvar.usd_rop1.usd.zip

Expected behavior

• We should see a colored Torus.
• The log should print "WARNING | /torus1/mesh_0: could not set ARRAY parameter "Pref""

[autodesk-oss-arnold-bot]

Issue synced internally to ARNOLD-13976

[autodesk-oss-arnold-bot]

Issue synced internally to ARNOLD-13981