Fix intermittent test failure in change 2246984

Sometimes the call to copyfile does not change the mtime on
the destination file, which causes the call to Reload to
be skipped. Force the reload to avoid this issue.

See #1852

(Internal change: 2247029)

pxr/usd/usd/testenv/testUsdFileFormats.py

@@ -244,7 +244,11 @@ def test_ReloadReplaceUsdUsdaWithUsdc(self):
             'usda')
 
         shutil.copyfile('crate.usd', 'test_replace.usd')
-        self.assertTrue(layer.Reload())
+
+        # Force a reload, otherwise the reload is skipped sometimes due
+        # to file mtimes not changing after copyfile.
+        self.assertTrue(layer.Reload(force=True))
+
         self.assertEqual(
             Usd.UsdFileFormat.GetUnderlyingFormatForLayer(layer), 
             'usdc')