Fix KCP remediation & add machine deployment remediation test

[nasusoba]

• Fix machine health check for controlplane
  • fix init lock release logic
  • add handling for remediation annotation and status
  • modify machine_controller logic to handle scenarios when machine.Status.NodeRef=nil
• Add 2 e2e tests:
  • kcp_remediation for controlplane remediation
  • md_remediation for machine deployment remediation
• Code cleanup
  • fix TODO for reconcileKubeConfig

Fixed #108