Update Ansible scheduler instructions

[hunhoffe]

Description

Update scheduler instructions based on recent commit (which rendered one step unnecessary) and add more information about using the scheduler without ElasticSearch.

Instructions tested in my local ansible setup on Ubuntu 20.04.

Related issue and scope

• I opened an issue to propose and discuss this change (New Scheduler with CouchDB backend #5223)

My changes affect the following components

• API
• Controller
• Message Bus (e.g., Kafka)
• Loadbalancer
• Scheduler
• Invoker
• Intrinsic actions (e.g., sequences, conductors)
• Data stores (e.g., CouchDB)
• Tests
• Deployment
• CLI
• General tooling
• Documentation

Types of changes

• Bug fix (generally a non-breaking change which closes an issue).
• Enhancement or new feature (adds new functionality).
• Breaking change (a bug fix or enhancement which changes existing behavior).

Checklist:

• I signed an Apache CLA.
• I reviewed the style guides and followed the recommendations (Travis CI will check :).
• I added tests to cover my changes.
• My changes require further changes to the documentation.
• I updated the documentation where necessary.

[codecov-commenter]

Codecov Report

Merging #5224 (480af99) into master (3e3414c) will increase coverage by 28.07%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master    #5224       +/-   ##
===========================================
+ Coverage   44.49%   72.57%   +28.07%     
===========================================
  Files         238      238               
  Lines       13957    13957               
  Branches      570      570               
===========================================
+ Hits         6210    10129     +3919     
+ Misses       7747     3828     -3919     

Impacted Files	Coverage Δ
...whisk/connector/kafka/KafkaProducerConnector.scala	55.00% <0.00%> (-25.00%)	⬇️
...whisk/connector/kafka/KafkaConsumerConnector.scala	59.15% <0.00%> (-22.54%)	⬇️
.../scala/org/apache/openwhisk/utils/Exceptions.scala	20.00% <0.00%> (-20.00%)	⬇️
...pache/openwhisk/core/invoker/InvokerReactive.scala	53.54% <0.00%> (-19.69%)	⬇️
...a/org/apache/openwhisk/http/BasicHttpService.scala	79.36% <0.00%> (-11.12%)	⬇️
...apache/openwhisk/core/ack/MessagingActiveAck.scala	58.33% <0.00%> (-8.34%)	⬇️
...pache/openwhisk/core/entity/ConcurrencyLimit.scala	88.23% <0.00%> (-5.89%)	⬇️
...pache/openwhisk/core/containerpool/Container.scala	85.05% <0.00%> (-5.75%)	⬇️
...sk/core/containerpool/docker/DockerContainer.scala	87.91% <0.00%> (-4.40%)	⬇️
...tainerpool/docker/DockerClientWithFileAccess.scala	92.00% <0.00%> (ø)
... and 133 more

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