[CRIU] [PATCH] restore: define root_as_sibling before using it

[Pavel Emelyanov]

>> Can we just drop the && all together?
> 
> IIRC the check for pdeath_sig was left not to restore every single
> process as criu's sibling. Smth wrong was with zdtm with it. Andrey
> should remember.

I remembered. We run test in 3.11 which prohibits simultaneous
use of CLONE_PARENT and CLONE_NEWPID. But zdtm.sh may run all
tests in pid namespace to avoid PIDs clashing on restore. Thus
we only do CLONE_PARENT for non-pdeath_sig-ed tasks to make
this work at all.

Thanks,
Pavel