Make it possible to compile with gcc4.6
diff --git a/test/cpp/qps/server.cc b/test/cpp/qps/server.cc
index 8e13634..be27c12 100644
--- a/test/cpp/qps/server.cc
+++ b/test/cpp/qps/server.cc
@@ -36,6 +36,8 @@
 #include <sys/signal.h>
 #include <thread>
 
+#include <unistd.h>
+
 #include <gflags/gflags.h>
 #include <grpc/support/alloc.h>
 #include <grpc/support/host_port.h>
@@ -97,7 +99,7 @@
 
 namespace {
 
-class TestServiceImpl final : public TestService::Service {
+class TestServiceImpl GRPC_FINAL : public TestService::Service {
  public:
   Status CollectServerStats(ServerContext* context, const StatsRequest*,
                             ServerStats* response) {
@@ -146,7 +148,7 @@
   grpc_profiler_start("qps_server.prof");
 
   while (!got_sigint) {
-    std::this_thread::sleep_for(std::chrono::seconds(5));
+    sleep(5);
   }
 
   grpc_profiler_stop();