UsdUvTexture should ignore missing textures in hydra

[sebastienblor]

UsdUvTexture shaders should implicitely ignore missing textures.
In the procedural we're forcing the arnold attribute "ignore_missing_textures" to be true for this shader, but this isn't done in the render delegate. This shows up in test_0175 in hydra mode

[autodesk-oss-arnold-bot]

Issue synced internally to ARNOLD-14054