Introduce SALT_VERSION var

As we plan to move to salt 2017.7 and at the same time
we need to check 2016.3 as well (and upgrdae path), introduce
new var SALT_VERSION with default value 2016.3

Also update repo path to salt from mirror mirantis and clened up
commented hacks

Reelated: PROD-19373

Change-Id: I3c327aa4b6369750f5bdabe1b96cb52ab5770f03
diff --git a/tcp_tests/templates/virtual-mcp10-dvr/underlay--user-data1604.yaml b/tcp_tests/templates/virtual-mcp10-dvr/underlay--user-data1604.yaml
index dcc77d2..3e0c1fd 100644
--- a/tcp_tests/templates/virtual-mcp10-dvr/underlay--user-data1604.yaml
+++ b/tcp_tests/templates/virtual-mcp10-dvr/underlay--user-data1604.yaml
@@ -59,8 +59,8 @@
    # saltstack repo is for minions that have the same version in the xenial and trusty (2016.3.3)
    #- echo "deb http://repo.saltstack.com/apt/ubuntu/16.04/amd64/latest xenial main" > /etc/apt/sources.list.d/saltstack.list
    #- wget -O - https://repo.saltstack.com/apt/ubuntu/16.04/amd64/latest/SALTSTACK-GPG-KEY.pub | apt-key add -
-   - echo "deb http://repo.saltstack.com/apt/ubuntu/16.04/amd64/2016.3 xenial main" > /etc/apt/sources.list.d/saltstack.list
-   - wget -O - https://repo.saltstack.com/apt/ubuntu/16.04/amd64/2016.3/SALTSTACK-GPG-KEY.pub | apt-key add -
+   - echo "deb http://repo.saltstack.com/apt/ubuntu/16.04/amd64/{{ SALT_VERSION }} xenial main" > /etc/apt/sources.list.d/saltstack.list
+   - wget -O - https://repo.saltstack.com/apt/ubuntu/16.04/amd64/{{ SALT_VERSION }}/SALTSTACK-GPG-KEY.pub | apt-key add -
 
    - apt-get clean
    - apt-get update