test: block prctl in seccomp_filter
test: block prctl in seccomp_filter

restore_creds uses prctl, so if we block this call in the seccomp filter
test, it causes things to fail (hang actually, seems we have some unhandled
error path here).

Signed-off-by: Tycho Andersen <10c18fcb898ee6b17d6575d444b125d10b3f4d6a@canonical.com>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@parallels.com>

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