parse_posix_timers should not call ferror if fopen returned NULL.
Reported-by: Adrian Reber <adrian@lisas.de>
Cc: Pavel Tikhomirov <snorcht@gmail.com>
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>