posix-timer: take into account that sival_ptr can be NULL (v3)
posix-timer: take into account that sival_ptr can be NULL (v3)

ID: 0
signal: 26/          (null)
notify: signal/pid.5954
ClockID: 1

fscanf "%p" doesn't handle "(null)".

https://bugzilla.openvz.org/show_bug.cgi?id=2894

v2: make the original scanf be %d/%s and then additionally
    parse the obtained string
v3: don't use strstr

Signed-off-by: Andrey Vagin <74c05afa918858348d6db8037d82fa8124870113@openvz.org>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@parallels.com>

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