[mitaka-trusty] Restore ability to deploy mitaka release on trusty

As maintenance team we still responsible for one mitaka-trusty cloud.
In case of incoming bugfix-request we need an ability to deploy mitaka
cluster using trusty-based mitaka packages and environment.

Some times ago (last successful run was Oct.9) this deployment were broken.
This was caused by removal of trusty iscsi daemon's name from formulas
(this was expectable but still painful).

To ensure that we will not get deployment errors like this (which will be
because trusty deployment even not legacy) we want to bind our deployment jobs
to last successful deployment than we can get. After some investigation this combination of
packages/formulas/model/deployment steps was found.

We want to use 2018.8.0 MCP release with some hacks inside tcp-qa deployment process.
This SHOULD NOT affects any existing deployment but will give us a chance to verify
shipped packages in the future.

Change-Id: I0d067c2c85a61714621aab6233dcfe79d55c4a18
diff --git a/tcp_tests/templates/virtual-mcp-trusty/Readme.txt b/tcp_tests/templates/virtual-mcp-trusty/Readme.txt
index fc9f978..da47d0b 100644
--- a/tcp_tests/templates/virtual-mcp-trusty/Readme.txt
+++ b/tcp_tests/templates/virtual-mcp-trusty/Readme.txt
@@ -2,4 +2,14 @@
 - virtual-mcp-mitaka-dvr-trusty
 - virtual-mcp-mitaka-ovs-trusty
 
-Used by maintenance team.
\ No newline at end of file
+Used by maintenance team.
+
+Use following env vars should be used:
+SALT_MODELS_COMMIT = 'fa85f84'
+SALT_MODELS_SYSTEM_TAG = '2018.8.0'
+REPOSITORY_SUITE = '2018.8.0'
+OVERRIDES = 'openstack_log_appender: true
+linux_system_repo_mk_openstack_version: testing
+'
+
+Also VCP 2018.8.0 images should be used
\ No newline at end of file