fix include names

cppcheck isn't smart enough to recognize these are c++ headers, not c
headers.  Considering we're already inconsistent about our naming, it's
easier to just be consistent, and move the last few files to use .hpp
instead of .h.

Tested:
Code builds, no changes.

Signed-off-by: Ed Tanous <ed@tanous.net>
Change-Id: Ic348d695f8527fa4a0ded53f433e1558c319db40
diff --git a/include/sessions.hpp b/include/sessions.hpp
index dc6ac1f..7cdb82a 100644
--- a/include/sessions.hpp
+++ b/include/sessions.hpp
@@ -1,9 +1,8 @@
 #pragma once
 
-#include "logging.h"
-#include "utility.h"
-
+#include "logging.hpp"
 #include "random.hpp"
+#include "utility.hpp"
 
 #include <openssl/rand.h>