Hydra mesh adapter doesn't convey time sampled values to render delegate

[marktucker]

Description of Issue

The hydra mesh adapter ignores time sampled indices attribute values on geometry subsets.

Steps to Reproduce

1. Load the attached USDA file into usdview:
   time_sampled_subset.zip
2. Switch to a render delegate that supports material assignments to geometry subsets.
3. Note that the whole sphere is green rather than being half red, because the geometry subset is reported to the render delegate as being empty because the subset only has a time sampled value, not a default value.

Package Versions

19.11

[jilliene]

Filed as internal issue #USD-5750