Automatic merge from submit-queue (batch tested with PRs 45040, 48960)
Do not generate warning event on dns search deduplication
In the case that the node is able to use the cluster DNS, `cluster.local` will already be in the node search domains in `/etc/resolv.conf`. The kubelet then parses `/etc/resolv.conf` on the node and combines it with $namespace.svc.$clusterDomain, svc.$clusterDomain, and $clusterDomain to create the pod DNS search domains. clusterDomain is `cluster.local` by default. This causes the code to generate a Warning event visible to the user for _every_ pod:
```
Warning DNSSearchForming Found and omitted duplicated dns domain in host search line: 'cluster.local' during merging with cluster dns domains
```
This is really overkill. IMHO, this should be done in the background with no user level notification or logging at all.
xref https://bugzilla.redhat.com/show_bug.cgi?id=1471198
@derekwaynecarr @eparis @vefimova
6fbc554c6b