Add chrono include to http/utility.hpp

In commit d139c2364bec98a5da1fe803414f3b02fdcd3092, http utility picked
up a dependency on chrono (for getting timestamps) but was relying on
another files include to function.  This adds the appropriate include.

Tested:
Code builds.  No functional changes.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I7c2353f2b5f991d78a76dbe19a0b55850c0126b9
diff --git a/http/utility.hpp b/http/utility.hpp
index 0a61f3f..be50636 100644
--- a/http/utility.hpp
+++ b/http/utility.hpp
@@ -4,6 +4,7 @@
 
 #include <openssl/crypto.h>
 
+#include <chrono>
 #include <cstdint>
 #include <cstring>
 #include <functional>