Enabling service's users in /etc/cron.allow

When https://gerrit.mcp.mirantis.net/25051 is merged only
users added to `linux:system:cron` pillar will be allowed
to use crontab tasks.

This commit adds the following users:
* aodh
* cassandra
* ceph
* elasticsearch
* glance
* keystone
* panko
* xtrabackup
* zookeeper

Enable managing cron packages/services and add 'root' user
to both `/etc/at.allow` and `/etc/cron.allow`.

Related-Prod: PROD-22546

Change-Id: Id543d0906842955c5632b1efa6985186afa6c9a9
diff --git a/keystone/server/fernet_rotation/cluster.yml b/keystone/server/fernet_rotation/cluster.yml
index a4aad33..7da8b5b 100644
--- a/keystone/server/fernet_rotation/cluster.yml
+++ b/keystone/server/fernet_rotation/cluster.yml
@@ -24,6 +24,10 @@
         credential_rotation_driver: ${_param:credential_rotation_driver}
   linux:
     system:
+      cron:
+        user:
+          keystone:
+            enabled: true
       job:
         keystone_fernet_rotate_rsync:
           command: '/var/lib/keystone/keystone_keys_rotate.sh -r -s -t fernet >> /var/log/keystone/keystone-rotate.log 2>> /var/log/keystone/keystone-rotate.log'
diff --git a/keystone/server/fernet_rotation/single.yml b/keystone/server/fernet_rotation/single.yml
index de5ca6a..bb6f234 100644
--- a/keystone/server/fernet_rotation/single.yml
+++ b/keystone/server/fernet_rotation/single.yml
@@ -10,6 +10,10 @@
         credential_rotation_driver: ${_param:credential_rotation_driver}
   linux:
     system:
+      cron:
+        user:
+          keystone:
+            enabled: true
       job:
         keystone_fernet_rotate_rsync:
           command: '/var/lib/keystone/keystone_keys_rotate.sh -r -t fernet >> /var/log/keystone/keystone-rotate.log 2>> /var/log/keystone/keystone-rotate.log'