Implement - bbctl preflight check

Things to check

• default storage class exists
• existence of metrics server (give warning if it does not exist) can check for CPU and MEMORY

  kubectl top node
  W1112 11:14:25.914957   16354 top_node.go:119] Using json format to get metrics. Next release will switch 
  to protocol-buffers, switch early by passing --use-protocol-buffers flag
  error: Metrics API not available

• verify that flux is installed
• OS configuration
  at least cover max_map_count for elasticsearch

out of scope

• kubenetes distro configuration