Replace glog and allow to reduce container privileges

[linki]

This replaces glog with github.com/kubermatic/glog-logrus which allows to inject a logrus logger instead (the default is a noop logger). Replacing glog allows us to set readOnlyRootFilesystem: true.

It also updates the example deployment file with all the settings recommended by https://kubesec.io/. Thanks to all the previous work: be able to run as non-root etc. (read-only fs was the last missing one).

Thanks to @kdomanski for github.com/kubermatic/glog-logrus.