chdir: need to check return value

otherwise it won't compile:

util.c: In function ‘cr_daemon’:
util.c:594:8: error: ignoring return value of ‘chdir’, declared
with attribute warn_unused_result [-Werror=unused-result]
   chdir("/");
        ^

Signed-off-by: Tikhomirov Pavel <snorcht@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>