[fix alibaba#909] fix compile error

`likely' and `unlikey' is also defined in dpdk or other project.
Declaration conflict occur when photonlibs and dpdk are compiled
together.

Signed-off-by: ivanallen <ivan_allen@163.com>

Author: ivanallen

common/utility.h

@@ -286,8 +286,13 @@ class OwnedPtr : OwnedPtr_Base
 	}
 */
 
+#ifndef likely
 constexpr bool likely(bool expr) { return __builtin_expect(expr, true); }
+#endif /* likely */
+
+#ifndef unlikely
 constexpr bool unlikely(bool expr) { return __builtin_expect(expr, false); }
+#endif /* unlikely */
 
 int version_compare(std::string_view a, std::string_view b, int& result);
 int kernel_version_compare(std::string_view dst, int& result);