Update CI config

[ArseniiPetrovich]

As for poanetwork/deployment-terraform#50 CI now requires additional environment variable that should be set by default.
Now jobs build and destroy should have additional lines in .circleci/config.yml
Before:

  destroy:
    docker:
      - image: poanetwork/terraform-prep
    working_directory: ~/deployment-terraform/azure

After:

  destroy:
    docker:
      - image: poanetwork/terraform-prep
    working_directory: ~/deployment-terraform/azure
    environment:
          ANSIBLE_AZURE_AUTH_SOURCE: env

[phahulin]

Resolved in #169