Replace all uses of NULL with nullptr

This was an automatic change made by clang-tidy.  It moves all uses of
NULL to nullptr, which are equivalent, but nullptr is prefered.

Tested:  Code compiles.

Signed-off-by: Ed Tanous <ed.tanous@intel.com>
Change-Id: I9526599b222693c9723a69934b599c7a5b5d1fbf
diff --git a/http/logging.h b/http/logging.h
index a608f1f..eb04cc1 100644
--- a/http/logging.h
+++ b/http/logging.h
@@ -27,7 +27,7 @@
     {
         std::string date;
         date.resize(32, '\0');
-        time_t t = time(0);
+        time_t t = time(nullptr);
 
         tm myTm{};