Make log file retention configurable

https://github.com/GoogleCloudPlatform/konlet/commit/25259e315c5c85e95d8322261d8f9a5b13001d54 added log rotation to the main container, but it's not possible to reduce or extend the amount of logs. It would be very helpful to be able to set those options.

GCP documentation suggests it's possible to configure logging options https://cloud.google.com/compute/docs/containers/configuring-options-to-run-containers#configuring_log_driver_options but these options don't affect the main container; the konlet supplied logging options win over options in daemon.json.

This request is similar to https://github.com/GoogleCloudPlatform/konlet/issues/56 but seems different enough to have its own issue.