TaskRunner starts the background thread only when needed.

Starts the background thread only if there are oneway methods.

Test: hidl_test
Test: boots
Change-Id: I71ee872c8513940f1f2a5cb052471a6a41f39fda
diff --git a/generateCpp.cpp b/generateCpp.cpp
index 881d31e..e38873c 100644
--- a/generateCpp.cpp
+++ b/generateCpp.cpp
@@ -1911,7 +1911,7 @@
     if (iface->hasOnewayMethods()) {
         out << "\n";
         out.indent([&] {
-            out << "mOnewayQueue.setLimit(3000 /* similar limit to binderized */);\n";
+            out << "mOnewayQueue.start(3000 /* similar limit to binderized */);\n";
         });
     }
     out << "}\n\n";