bmcweb: fix the random headers

bmcweb::OpenSSLGenerator is defined in include/random.hpp.

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: I1d8751b49a0121526a40b885ed7f5b520640f9f0
diff --git a/include/sessions.hpp b/include/sessions.hpp
index b0d6ca7..13a335a 100644
--- a/include/sessions.hpp
+++ b/include/sessions.hpp
@@ -13,6 +13,7 @@
 #include <dbus_singleton.hpp>
 #include <nlohmann/json.hpp>
 #include <pam_authenticate.hpp>
+#include <random.hpp>
 #include <sdbusplus/bus/match.hpp>
 
 #include <csignal>