[quickstart] Fix a couple typos in the NiFi guide
[quickstart] Fix a couple typos in the NiFi guide

Changes cluster to container given Nifi is a single
node in this example.

Change-Id: I008ef2550edea06dafb58bc7e8e408e57d255269
Reviewed-on: http://gerrit.cloudera.org:8080/13964
Tested-by: Grant Henke <4cf7ebbe638391c4d27a10cf751b99bdbd1a1880@apache.org>
Reviewed-by: Andrew Wong <b68e4fdc6430321a6b47400732ff97d7ae91234e@cloudera.com>

helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu,helifu/kudu