First-time tutorials import from k/examples (#4353)

This imports the tutorials from kubernetes/examples repository for the first
time. It adds "DO NOT UPDATE" notices and updates some titles. These tutorials
will be maintained at k/examples repository.

Also fixing a bug in the update script (we were inserting the `<!--` comments
before the metadata section on the top, causing articles to render incorrectly).

Signed-off-by: Ahmet Alp Balkan <ahmetb@google.com>

docs/tutorials/stateful-application/cassandra.md

@@ -2,6 +2,43 @@
 title: "Example: Deploying Cassandra with Stateful Sets"
 ---
 
+<!--
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+DO NOT UPDATE THIS FILE!
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+Submit a patch to https://github.com/kubernetes/examples and
+once it is merged, run ./update-imported-tutorials.sh to
+import it to the website.
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+-->
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 ## Table of Contents
 
   - [Prerequisites](#prerequisites)
@@ -835,7 +872,7 @@ via a replication control or a daemonset, you will need to use the custom seed p
 In Cassandra, a `SeedProvider` bootstraps the gossip protocol that Cassandra uses to find other
 Cassandra nodes. Seed addresses are hosts deemed as contact points. Cassandra
 instances use the seed list to find each other and learn the topology of the
-ring. The [`KubernetesSeedProvider`](https://github.com/kubernetes/kubernetes/blob/master/examples/storage/cassandra/java/src/main/java/io/k8s/cassandra/KubernetesSeedProvider.java)
+ring. The [`KubernetesSeedProvider`](https://github.com/kubernetes/examples/blob/master/cassandra/java/src/main/java/io/k8s/cassandra/KubernetesSeedProvider.java)
 discovers Cassandra seeds IP addresses via the Kubernetes API, those Cassandra
 instances are defined within the Cassandra Service.
 
@@ -856,4 +893,4 @@ manager that we need 0.1 cpu (0.1 core).
 
 <!-- BEGIN MUNGE: GENERATED_ANALYTICS -->
 [![Analytics](https://kubernetes-site.appspot.com/UA-36037335-10/GitHub/cassandra/README.md?pixel)]()
-<!-- END MUNGE: GENERATED_ANALYTICS -->
+<!-- END MUNGE: GENERATED_ANALYTICS -->