fixup! fixup! USDLayerWriter : Pre-process scene for improved perform…

…ance

We can't let the job linger in the default job pool, as that causes failures in later tests that assert there are no zombie jobs.

python/GafferUSDTest/USDLayerWriterTest.py

@@ -411,7 +411,7 @@ def testDispatch( self ) :
 		script["writer"]["layer"].setInput( script["reader"]["out"] )
 		script["writer"]["fileName"].setValue( self.temporaryDirectory() / "test.usda" )
 
-		script["dispatcher"] = GafferDispatch.LocalDispatcher()
+		script["dispatcher"] = GafferDispatch.LocalDispatcher( jobPool = GafferDispatch.LocalDispatcher.JobPool() )
 		script["dispatcher"]["tasks"][0].setInput( script["writer"]["task"] )
 		script["dispatcher"]["jobsDirectory"].setValue( self.temporaryDirectory() / "localJobs" )
 		script["dispatcher"]["task"].execute()