Automatic merge from submit-queue
rkt: Replace 'journalctl' with rkt's GetLogs() API.
This replaced the `journactl` shell out with rkt's GetLogs() API.
Fixes#26997
To make this fully work, we need rkt to have this patch #https://github.com/coreos/rkt/pull/2763
cc @kubernetes/sig-node @euank @alban @iaguis @jonboulle