core+daemon: eliminate scheduler::{schedule,cancel} wrappers

Also move core/global-io.hpp to daemon/global.hpp

Refs: #4528, #4883
Change-Id: I0b99029f1a19d7451aab57099cd3303b7eb42ff3
diff --git a/tests/daemon/mgmt/rib-manager-sl-announce.t.cpp b/tests/daemon/mgmt/rib-manager-sl-announce.t.cpp
index 452d758..5576878 100644
--- a/tests/daemon/mgmt/rib-manager-sl-announce.t.cpp
+++ b/tests/daemon/mgmt/rib-manager-sl-announce.t.cpp
@@ -163,7 +163,7 @@
 
 private:
   ndn::util::DummyClientFace m_face;
-  ndn::util::Scheduler m_scheduler;
+  Scheduler m_scheduler;
   ndn::nfd::Controller m_nfdController;
   Dispatcher m_dispatcher;
   rib::FibUpdater m_fibUpdater;