daemonize(): fix warning, output diagnostic message in case of failure
daemonize(): fix warning, output diagnostic message in case of failure

daemon.c: In function 'daemonize':
daemon.c:83:5: warning: ignoring return value of 'chdir', declared with
attribute warn_unused_result [-Wunused-result]

ryd/chaosvpn,ryd/chaosvpn,ryd/chaosvpn