refresh cassandra repo

  * Mark few files like depracated
  * Add corresponding debmirror

Related-Bug: PROD-17862 (PROD:17862)

Change-Id: Ie44ed9400ab714582e62a2e733f3f574c315736e
diff --git a/linux/system/repo_local/ubuntu.yml b/linux/system/repo_local/ubuntu.yml
index e93a4b3..e5b940a 100644
--- a/linux/system/repo_local/ubuntu.yml
+++ b/linux/system/repo_local/ubuntu.yml
@@ -1,3 +1,5 @@
+# DEPRECATED since 2018.7+ release.
+# Please use system/repo/mcp/apt_mirantis
 parameters:
   linux:
     system: