Fixes #4711 - add a namespace configuration option to KCF

[mcdan]

A fix for #4711

Description

This change forces the k8s client to use a particular namespace when communicating with the API server.

Related issue and scope

• I opened an issue to propose and discuss this change (Namespace errors from k8s client when namespace not set #4711)

My changes affect the following components

• API
• Controller
• Message Bus (e.g., Kafka)
• Loadbalancer
• 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-io]

Codecov Report

Merging #4712 into master will decrease coverage by 6.66%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #4712      +/-   ##
==========================================
- Coverage   84.98%   78.32%   -6.67%     
==========================================
  Files         191      198       +7     
  Lines        8574     8829     +255     
  Branches      599      611      +12     
==========================================
- Hits         7287     6915     -372     
- Misses       1287     1914     +627

Impacted Files	Coverage Δ
...re/containerpool/kubernetes/KubernetesClient.scala	26.66% <100%> (+1.1%)	⬆️
...core/database/cosmosdb/RxObservableImplicits.scala	0% <0%> (-100%)	⬇️
...enwhisk/connector/kafka/KamonMetricsReporter.scala	0% <0%> (-100%)	⬇️
...e/database/cosmosdb/cache/ChangeFeedConsumer.scala	0% <0%> (-100%)	⬇️
...ore/database/cosmosdb/cache/CacheInvalidator.scala	0% <0%> (-100%)	⬇️
...core/database/cosmosdb/CosmosDBArtifactStore.scala	0% <0%> (-96.23%)	⬇️
...sk/core/database/cosmosdb/CosmosDBViewMapper.scala	0% <0%> (-93.8%)	⬇️
...tabase/cosmosdb/cache/CacheInvalidatorConfig.scala	0% <0%> (-92.31%)	⬇️
...e/database/cosmosdb/cache/KafkaEventProducer.scala	0% <0%> (-77.78%)	⬇️
...whisk/core/database/cosmosdb/CosmosDBSupport.scala	0% <0%> (-74.08%)	⬇️
... and 21 more

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