check: try to call clone with CLONE_NEWPID and CLONE_PARENT

This combination was forbidden in 3.12
commit 40a0d32d1eaffe6aac7324ca92604b6b3977eb0e :
"fork: unify and tighten up CLONE_NEWUSER/CLONE_NEWPID checks"

and then it was permited again in 3.13:
commit 1f7f4dde5c945f41a7abc2285be43d918029ecc5
fork:  Allow CLONE_PARENT after setns(CLONE_NEWPID)

Cc: Adrian Reber <adrian@lisas.de>
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>