Tuning sysctl for all node

Tuning sysctl on all nodes.

The tuning factors and values are reference from:
https://opendev.org/openstack/charm-ceph-osd/src/branch/master/lib/charms_ceph/utils.py#L115-L144
diff --git a/playbooks/kubernetes.yml b/playbooks/kubernetes.yml
index ebd5dc1..6761047 100644
--- a/playbooks/kubernetes.yml
+++ b/playbooks/kubernetes.yml
@@ -15,6 +15,7 @@
 - hosts: all
   become: true
   roles:
+    - role: sysctl
     - role: ethtool
       tags:
         - ethtool