parasite: don't block if a parasite crashes
parasite: don't block if a parasite crashes

We need to detect parasite crashes to not hangs on socket operations.
CRIU ptraces parasite. So if it crashes, SIGCHLD is received.

If a parasite daemon crashed, we can to do nothing. The state of current
process can't be restored, because we can't to drop the signal. The
state of other processes are consistent. Probably the best choise in
this case is to exit.

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

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