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/common/ubuntu_salt_bootstrap.sh b/common/ubuntu_salt_bootstrap.sh
index e923866..e0e5ff4 100644
--- a/common/ubuntu_salt_bootstrap.sh
+++ b/common/ubuntu_salt_bootstrap.sh
@@ -6,20 +6,20 @@
 fi
 #
 CLUSTER_NAME=${CLUSTER_NAME:-lost_cluster_name_variable}
-FORMULA_VERSION=${FORMULA_VERSION:-testing}
+MCP_VERSION=${MCP_VERSION:-testing}
 SALTSTACK_GPG=${SALTSTACK_GPG:-"https://repo.saltstack.com/apt/ubuntu/16.04/amd64/2017.7/SALTSTACK-GPG-KEY.pub"}
 SALTSTACK_REPO=${SALTSTACK_REPO:-"http://repo.saltstack.com/apt/ubuntu/16.04/amd64/2017.7 xenial main"}
 APT_MIRANTIS_GPG=${APT_MIRANTIS_GPG:-"http://apt.mirantis.com/public.gpg"}
-APT_MIRANTIS_SALT_REPO=${APT_MIRANTIS_SALT_REPO:-"http://apt.mirantis.com/xenial/ $FORMULA_VERSION salt"}
+APT_MIRANTIS_SALT_REPO=${APT_MIRANTIS_SALT_REPO:-"http://apt.mirantis.com/xenial/ $MCP_VERSION salt"}
 
 function process_repos(){
 # TODO: those  should be unhardcoded and re-writed, using CC model
 wget -O - ${SALTSTACK_GPG} | sudo apt-key add -
 wget -O - ${APT_MIRANTIS_GPG} | apt-key add -
-wget -O - http://mirror.mirantis.com/${FORMULA_VERSION}/extra/xenial/archive-extra.key | apt-key add -
+wget -O - http://mirror.mirantis.com/${MCP_VERSION}/extra/xenial/archive-extra.key | apt-key add -
 
 echo "deb [arch=amd64] ${SALTSTACK_REPO}"  > /etc/apt/sources.list.d/mcp_saltstack.list
-echo "deb [arch=amd64] http://mirror.mirantis.com/${FORMULA_VERSION}/extra/xenial xenial main"  > /etc/apt/sources.list.d/mcp_extra.list
+echo "deb [arch=amd64] http://mirror.mirantis.com/${MCP_VERSION}/extra/xenial xenial main"  > /etc/apt/sources.list.d/mcp_extra.list
 
 # This Pin-Priority fix should be always aligned with
 # https://github.com/Mirantis/reclass-system-salt-model/blob/master/linux/system/repo/mcp/apt_mirantis/saltstack.yml