libct/cg/fscommon: log openat2 init failures
libct/cg/fscommon: log openat2 init failures

In case we get ENOSYS from openat2(2), this is expected, so log that
we're falling back to using securejoin as debug.

Otherwise, log it as a warning (as the error is unexpected, but we're
still good to go).

Signed-off-by: Kir Kolyshkin <3a017b8ddb3f9cf3e4a59978b004111bdeb97f08@gmail.com>

xiaochenshen/runc,rhatdan/runc,estesp/runc,kolyshkin/runc,dqminh/runc,rhatdan/runc,estesp/runc,opencontainers/runc,opencontainers/runc,xiaochenshen/runc,rhatdan/runc,kolyshkin/runc,opencontainers/runc,xiaochenshen/runc,dqminh/runc,kolyshkin/runc,estesp/runc,rhatdan/runc,dqminh/runc,opencontainers/runc,kolyshkin/runc,dqminh/runc