Add salt-formulas repo

  * Correct pinning
  * At mirror.mirantis.com
  * Unclude update|hotfix stubs

Prod-related: PROD-25034 (PROD:25034)

Change-Id: I3d776ac1d9b15187ae9920be476f14cfcccec969
diff --git a/defaults/linux_system_repo.yml b/defaults/linux_system_repo.yml
index b889b0f..880194f 100644
--- a/defaults/linux_system_repo.yml
+++ b/defaults/linux_system_repo.yml
@@ -24,6 +24,10 @@
     linux_system_repo_mcp_saltstack_url: ${_param:linux_system_repo_url}/saltstack-${_param:linux_system_repo_mcp_saltstack_version_number}/
     linux_system_repo_mcp_fluentd_url: ${_param:linux_system_repo_url}/td-agent/
     #
+    linux_system_repo_mcp_salt_url: ${_param:linux_system_repo_url}/salt-formulas/
+    linux_system_repo_update_mcp_salt_url: ${_param:linux_system_repo_update_url}/salt-formulas/
+    linux_system_repo_hotfix_mcp_salt_url: ${_param:linux_system_repo_hotfix_url}/salt-formulas/
+    #
     linux_system_repo_mirantis_openstack_url: ${_param:linux_system_repo_url}/openstack-${_param:openstack_version}/
     linux_system_repo_update_mirantis_openstack_url: ${_param:linux_system_repo_update_url}/openstack-${_param:openstack_version}/
     linux_system_repo_hotfix_mirantis_openstack_url: ${_param:linux_system_repo_hotfix_url}/openstack-${_param:openstack_version}/