Use s.c_str() in log messages

Fixes issues with data passed to phosphor::logging::log(entry()).
This is part of a series of commits that resolves openbmc 2905.

Tested: static_assert only

Change-Id: I9fac771f54e4acbec97ce1360c106b6e3eb4fe9d
Signed-off-by: Joseph Reynolds <jrey@us.ibm.com>
diff --git a/read_fru_data.cpp b/read_fru_data.cpp
index a1bced9..5133612 100644
--- a/read_fru_data.cpp
+++ b/read_fru_data.cpp
@@ -55,8 +55,8 @@
     {
         //If property is not found simply return empty value
         log<level::ERR>("Error in reading property values from inventory",
-                        entry("INTERFACE=%s", intf),
-                        entry("PATH=%s", objPath));
+                        entry("INTERFACE=%s", intf.c_str()),
+                        entry("PATH=%s", objPath.c_str()));
         return properties;
     }
     reply.read(properties);