start_ccm_cluster: take env var for aws region (#794)
start_ccm_cluster: take env var for aws region (#794)


mesosphere/dcos-cli,kensipe/dcos-cli,mesosphere/dcos-cli,dcos/dcos-cli,dcos/dcos-cli,kensipe/dcos-cli,kensipe/dcos-cli,dcos/dcos-cli,dcos/dcos-cli,kensipe/dcos-cli,mesosphere/dcos-cli,dcos/dcos-cli,kensipe/dcos-cli