rib: make Service globally accessible via get() static function

Change-Id: I2101fb81a613d301acbce7f26e062caa692c5e29
Refs: #4683
diff --git a/core/global-io.hpp b/core/global-io.hpp
index f9abccf..ab0e17c 100644
--- a/core/global-io.hpp
+++ b/core/global-io.hpp
@@ -42,10 +42,10 @@
 void
 runOnRibIoService(const std::function<void()>& f);
 
-#ifdef WITH_TESTS
 boost::asio::io_service&
 getRibIoService();
 
+#ifdef WITH_TESTS
 /** \brief delete the global io_service instance
  *
  *  It will be recreated at the next invocation of getGlobalIoService.