Small refactoring for packer scripts

* Get rid of formula version variable and use MCP_VERSION instead
* Remove docker images pull
* Remove adding of jenkins theme b/c it's already inside docker image
* Move flag for jenkins in docker to /opt

Closes-task: #PROD-24048 (PROD:24048)
Change-Id: I41a1c4771d9cf890bd371264a35727ded6fc52a8
diff --git a/mirror-image/scripts/mirrors.sh b/mirror-image/scripts/mirrors.sh
index 67cf90c..bdf686e 100644
--- a/mirror-image/scripts/mirrors.sh
+++ b/mirror-image/scripts/mirrors.sh
@@ -26,7 +26,7 @@
 # Those would prevent failures for 2018q3+ model releases, where
 # 'system.linux.system.repo.mcp.apt_mirantis.update.xxx' enabled by default
 pushd /srv/volumes/aptly/public/
-  CUR_V=$(salt-call pillar.get _param:apt_mk_version --out text | awk '{print $2}')
+  CUR_V=$(salt-call pillar.get _param:mcp_version --out text | awk '{print $2}')
   mkdir -p update
   ln -s ../${CUR_V} update/${CUR_V} || true
 popd