Preconfigure PKE in pre-cached images

[sagikazarmark]

Is your feature request related to a problem? Please describe.
When creating a cluster using a pre-cached image with PKE already installed, I don't want:

• PKE to be installed again
• Container runtime and Kubernetes installed again
• Container runtime and Kubernetes configured again

Describe the solution you'd like to see
Store some PKE configuration in images that PKE can use to configure the node (eg. container runtime). This configuration could be created by a user data script on base images without PKE.

[sagikazarmark]

Config (eg. /etc/banzaicloud/pke.yaml):

kubernetes:
    version: 1.18.2
    installed: true

containerRuntime:
    type: docker
    installed: true

Machine image: generate config
User data script: generate config if not already present
PKE command: do not use the above flags