cgroup2: use CRIU's new freezer v2 support
cgroup2: use CRIU's new freezer v2 support

The newest CRIU version supports freezer v2 and this tells runc
to use it if new enough or fall back to non-freezer based process
freezing on cgroup v2 system.

Signed-off-by: Adrian Reber <9f82b3db7475afbb412180fe9fab7c69d6ece340@redhat.com>

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