Unified multiple definitions of container_of() macro.

Removed duplicate definitions of the container_of() macro and
refactored sources to use the single implementation.

Signed-off-by: Jon A. Cruz <jonc@osg.samsung.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>
diff --git a/tests/ivi_layout-test-plugin.c b/tests/ivi_layout-test-plugin.c
index c39a714..b4abfbf 100644
--- a/tests/ivi_layout-test-plugin.c
+++ b/tests/ivi_layout-test-plugin.c
@@ -35,6 +35,7 @@
 #include "weston-test-server-protocol.h"
 #include "ivi-test.h"
 #include "ivi-shell/ivi-layout-export.h"
+#include "shared/helpers.h"
 
 struct test_context;