libct/logs: parse log level implicitly
libct/logs: parse log level implicitly

There's no need to call logrus.ParseLevel as logrus.Level already
implements encoding.TextUnmarshaler interface.

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

opencontainers/runc,rhatdan/runc,opencontainers/runc,rhatdan/runc,opencontainers/runc,opencontainers/runc,kolyshkin/runc,kolyshkin/runc,rhatdan/runc,rhatdan/runc,kolyshkin/runc,kolyshkin/runc