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>
7 files changed