In case of daemonize, use the logfile passed with the -D option in
order to redirect stderr to it instead of /dev/null.

Also remove some unused code in log.h.

Signed-off-by: Dimitris Aragiorgis <dimara@arrikto.com>
Message-Id: <1455795518-19205-1-git-send-email-dimara@arrikto.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>