Fix globe anchors on prims that don't have all xform ops set

[lilleyse]

Globe anchors were only working on prims that had either all xform ops set or no xform ops set.

The code below where only the translation is set now works:

from cesium.usd.plugins.CesiumUsdSchemas import CartographicPolygon
from asyncio import ensure_future
from pxr import UsdGeom

polygon_path = "/polygon"
ctx = omni.usd.get_context()
stage = ctx.get_stage()
polygon = CartographicPolygon.Define(stage, polygon_path)
polygon_prim = polygon.GetPrim()
xformCommonApi = UsdGeom.XformCommonAPI(polygon_prim)
xformCommonApi.SetTranslate((10, 0, 0))