Refactor keystorage and arond.

   * Move key's to soft-param
   * Using link-structure, aka ${linux:XXX:key}
     broke some formulas logic

Closes-Bug: PROD-23577 (PROD:23577)

Change-Id: I81dc528372ec73ac7650f921fc5df76a8ee2027a
diff --git a/linux/system/repo/mcp/apt_mirantis/cassandra.yml b/linux/system/repo/mcp/apt_mirantis/cassandra.yml
index e29a220..1136a85 100644
--- a/linux/system/repo/mcp/apt_mirantis/cassandra.yml
+++ b/linux/system/repo/mcp/apt_mirantis/cassandra.yml
@@ -13,6 +13,7 @@
           source: "deb [arch=amd64] ${_param:linux_system_repo_mcp_cassandra_url}/${_param:linux_system_codename}/ ${_param:linux_system_repo_mcp_cassandra_version} main"
           architectures: amd64
           clean_file: true
+          key: ${_param:linux_system_repo_mcp_cassandra_key}
           pin:
           - pin: 'release o=Apache Cassandra Packages'
             priority: 1100