Fix crash on It2Me host.

This is a regression from https://codereview.chromium.org/1530523002.
We should be passing signal_strategy_.get() instead of signal_strategy.get()
to the underlying JingleSessionManager in
it2me_host.cc

BUG=579758

Review URL: https://codereview.chromium.org/1638733002

Cr-Commit-Position: refs/heads/master@{#371452}

remoting/host/it2me/it2me_host.cc

@@ -243,7 +243,7 @@ void It2MeHost::FinishConnect() {
           network_settings, protocol::TransportRole::SERVER);
 
   scoped_ptr<protocol::SessionManager> session_manager(
-      new protocol::JingleSessionManager(signal_strategy.get()));
+      new protocol::JingleSessionManager(signal_strategy_.get()));
 
   scoped_ptr<protocol::CandidateSessionConfig> protocol_config =
       protocol::CandidateSessionConfig::CreateDefault();