thread-pool: Initialize empty pools to start complete.

Otherwise waiting for completion if we push no work hangs.

Change-Id: I7103bdb779eb66a65cd8496091e72a0c65eb3567

comphelper/source/misc/threadpool.cxx

@@ -99,7 +99,7 @@ ThreadPool::ThreadPool( sal_Int32 nWorkers ) :
     for( sal_Int32 i = 0; i < nWorkers; i++ )
         maWorkers.push_back( new ThreadWorker( this ) );
 
-    maTasksComplete.reset();
+    maTasksComplete.set();
 
     osl::MutexGuard aGuard( maGuard );
     for( size_t i = 0; i < maWorkers.size(); i++ )