IceTransport: move callback in setOnShutdown

Change-Id: Iacd7f4a80378a4e0c17821bc217e2a073ab8fb70
diff --git a/src/ice_transport.cpp b/src/ice_transport.cpp
index a735e75..302afb1 100644
--- a/src/ice_transport.cpp
+++ b/src/ice_transport.cpp
@@ -1662,7 +1662,7 @@
 void
 IceTransport::setOnShutdown(onShutdownCb&& cb)
 {
-    pimpl_->scb = cb;
+    pimpl_->scb = std::move(cb);
 }
 
 ssize_t