Fix excluded prim paths

[csyshing]

Ensure excluded prims (that do not need to be rendered) handled properly so that we don't get double up geo on viewport.

[csyshing]

I checked the unit test log, the message is about schema generation error during configuration, on Windows + Maya 2019 only:

    Traceback (most recent call last):
      File "P:/shared/Artifactory/Windows/USD/4ae4ff5/bin/usdGenSchema", line 48, in <module>
        from pxr import Plug, Sdf, Usd, Vt, Tf
      File "P:\shared\Artifactory\Windows\USD\4ae4ff5\lib\python\pxr\Plug\__init__.py", line 29, in <module>
        Tf.PreparePythonModule()
      File "P:\shared\Artifactory\Windows\USD\4ae4ff5\lib\python\pxr\Tf\__init__.py", line 89, in PreparePythonModule
        "." + moduleName, f_locals["__name__"])
      File "P:\shared\Artifactory\Windows\rundev-2019\202003131251\runtime\155eb96\runTime\bin\python27.zip\importlib\__init__.py", line 37, in import_module
    ImportError: DLL load failed: The specified procedure could not be found.
    CMake Error at lib/usd/schemas/CMakeLists.txt:139 (message):
      Schemas generation failed

All other build variants passed file.

I am not quite sure why this PR is causing such an error on Windows + Maya 2019 ?

[seando-adsk]

@csyshing The 2019 build problem is a fault with our internal builds. I'm fixing it now, then we'll merge your PR.