logging: pass binary name not logfile name when enabling logging

logging: pass binary name not logfile name when enabling logging

Instead of having each caller pass in the desired logfile name, pass in
the binary name instead. The logging code can then just derive a logfile
name by appending ".log".

Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>