Use s.c_str() in log messages

Partly Resolves openbmc/openbmc 2905

Tested: static_assert only

Change-Id: I9a97938e62ba4c285ef1f4fae36012e26f2e5170
Signed-off-by: Joseph Reynolds <jrey@us.ibm.com>
diff --git a/policy_find.cpp b/policy_find.cpp
index b8b671a..7833cfa 100644
--- a/policy_find.cpp
+++ b/policy_find.cpp
@@ -158,7 +158,7 @@
         {
             using namespace phosphor::logging;
             log<level::ERR>("Invalid PROCEDURE value found",
-                            entry("PROCEDURE=%s", *mod));
+                            entry("PROCEDURE=%s", mod->c_str()));
         }
     }