Initialize channel information on Init().

The channel information returned by dbus_service relies on the
OmahaRequestParams object being initialized, which didn't happen until
the first update check. This patch also fixes the store of the newly
selected channel.

Bug: chromium:551605,chromium:548486
TEST=deployed update_engine to a link device. Changed channels right after reboot.

Change-Id: I5070b3f8f09fc2ac5a74e2d40df9a2bea92df019
diff --git a/real_system_state.cc b/real_system_state.cc
index cf904c2..8efb903 100644
--- a/real_system_state.cc
+++ b/real_system_state.cc
@@ -102,6 +102,15 @@
     system_rebooted_ = true;
   }
 
+  // Initialize the OmahaRequestParams with the default settings. These settings
+  // will be re-initialized before every request using the actual request
+  // options. This initialization here pre-loads current channel and version, so
+  // the DBus service can access it.
+  if (!request_params_.Init("", "", false)) {
+    LOG(WARNING) << "Ignoring OmahaRequestParams initialization error. Some "
+                    "features might not work properly.";
+  }
+
   // Initialize the Update Manager using the default state factory.
   chromeos_update_manager::State* um_state =
       chromeos_update_manager::DefaultStateFactory(