shill: Add a mockable layer for socket.h.

Mock the layer in device_info_unittest.cc. Some cleanup.

BUG=chromium-os:17394
TEST=unit tests

Change-Id: I2ddcb2fd0e01418a463596bf4e3a804b3e3023b2
Reviewed-on: http://gerrit.chromium.org/gerrit/3807
Reviewed-by: Darin Petkov <petkov@chromium.org>
Tested-by: Darin Petkov <petkov@chromium.org>
diff --git a/shill_main.cc b/shill_main.cc
index 0039e09..0a09267 100644
--- a/shill_main.cc
+++ b/shill_main.cc
@@ -15,6 +15,7 @@
 #include "shill/dbus_control.h"
 #include "shill/dhcp_provider.h"
 #include "shill/glib.h"
+#include "shill/shill_config.h"
 #include "shill/shill_daemon.h"
 
 using std::string;