Upgrade Dockerfile to use terraform 0.12.6

Author: Constantin Muraru

build_scripts/Dockerfile

@@ -1,5 +1,5 @@
 FROM python:2.7.16-alpine3.9 AS compile-image
-ARG TERRAFORM_VERSION="0.12.5"
+ARG TERRAFORM_VERSION="0.12.6"
 ARG AZURE_CLI_VERSION="2.0.67"
 
 ENV BOTO_CONFIG=/dev/null
@@ -23,7 +23,7 @@ RUN apk del --purge build
 
 
 FROM python:2.7.16-alpine3.9
-ARG TERRAFORM_VERSION="0.12.5"
+ARG TERRAFORM_VERSION="0.12.6"
 ARG VAULT_VERSION="1.1.3"
 ARG KUBECTL_VERSION="v1.13.7"
 ARG AWS_IAM_AUTHENTICATOR_VERSION="1.13.7/2019-06-11"