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/host-interface.cpp b/host-interface.cpp
index 19ca291..8663929 100644
--- a/host-interface.cpp
+++ b/host-interface.cpp
@@ -57,7 +57,7 @@
 
     log<level::DEBUG>("Pushing cmd on to queue",
             entry("CONTROL_HOST_CMD=%s",
-                  convertForMessage(command)));
+                  convertForMessage(command).c_str()));
 
     auto cmd = std::make_tuple(ipmiCommand.at(command),
                         std::bind(&Host::commandStatusHandler,