fix for cp4na issue 264: dynamic value population for readyCheck

[dushyantbehl]

Added support for dynamic value population in check ready script and it's name.
Also added a unit test for the same.

Tested with following example on CP4NA v2.1 -

compose:
  - name: Create
    deploy:
      - helm:
          chart: apache-7.3.15.tgz
          name: r{{ system_properties.resource_id_label }}
          namespace: default
          values: "apache-helm-chart-values.yaml"
    checkReady:
      script: "{{ nameCheck }}.py"

[dvaccarosenna]

Fixes #46