Revert "Add known issue on PDBs and certificate rotation (backport)"

This reverts commit a48569b.

Author: Maleware

modules/concepts/pages/operations/pod_disruptions.adoc

@@ -117,37 +117,3 @@ This PDB allows only one Pod out of all the Namenodes and Journalnodes to be dow
 
 == Details
 Have a look at the xref:contributor:adr/ADR030-allowed-pod-disruptions.adoc[ADR on Allowed Pod disruptions] for the implementation details.
-
-== Known issue with PDBs and certificate rotations
-PDBs together with certificate rotations can be problematic in case e.g. {commons-operator}[commons-operator] was unavailable to restart the Pods before the certificate expire.
-commons-operator uses the `evict` API in Kubernetes, which respects the PDB.
-If a Pod is evicted and a PDB would be violated, the Pod is *not* restarted.
-Assume a product like xref:zookeeper:index.adoc[Apache ZooKeeper] which needs to form a quorum to function and the PDB only allows a single Pod to be unavailable.
-As soon as enough certificates of the ZookeeperCluster have expired, all Pods will crash-loop, as they encounter expired certificates.
-As only the container crash-loops (not the entire Pod), no new certificate is issued.
-As soon as commons-operator comes online again it tries to `evict` a Zookeeper Pod.
-However, this is prohibited, as the PDB would be violated.
-
-NOTE: We encountered this problem only with the specific outlined case above and only under this circumstances.
-
-=== Workaround
-If you encounter this only manually deleting those pods can help out of this situation.
-A Pod deletion (other than evictions) does *not* respect PDBs, so the Pods can be restarted anyway.
-All restarted Pods will get a new certificate, the stacklet should turn healthy again.
-
-=== Restore working state
-Delete pods with e.g. `kubectl``.
-[source, bash]
-----
-kubectl delete pod -l app.kubernetes.io/name=zookeeper,app.kubernetes.io/instance=simple-zk
-pod "simple-zk-server-default-0" deleted
-pod "simple-zk-server-default-1" deleted
-pod "simple-zk-server-default-2" deleted
-----
-
-
-=== Preventing this situation
-The best measure is to make sure that commons-operator is always running, so that it can restart the Pods before the certificates expire.
-
-A hacky way to prevent this situation could be to disable PDBs for the specific stacklet.
-But this also has the downside, that you are now missing the benefits of the PDB.