Move Docker version variable in Dockerfile

.gitlab-ci.yml

@@ -24,7 +24,6 @@ variables:
   GIT_AUTHOR_EMAIL: "gitlab@runner"
   NUM_SERVER_TO_KEEP: 5
   NUM_IMAGE_TO_KEEP: 30
-  PACKER_VER: 1.8.3
   PKR_VAR_root_ssh_key: "ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBAFqqWgmYpEaGtHBeTu27ntVJpYjwq/x5aBefrvfhk8Z9lE3cuZ26vJ9n/9tGE4Zn2Pew1mpZgi6PzfJ3vMt8yA= root@master"
   DEV_KEY: "ssh-rsa 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 louistw@uab.edu"
 

Dockerfile

@@ -4,6 +4,7 @@ ENV S3CMD_VER=2.3.0
 ENV ANSIBLE_VER=4.10.0
 ENV OSC_VER=5.8.0
 ENV TF_VER=1.4.6
+ENV PACKER_VER=1.8.3
 
 RUN apt-get update && apt-get install --no-install-recommends -y \
     git \