Remove containers gradually when disable invoker

[jiangpengcheng]

Don't remove lots of containers/pods at once to avoid overload

Description

Related issue and scope

• I opened an issue to propose and discuss this change (#????)

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 #5253 (daf7c53) into master (0c4aab1) will increase coverage by 2.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #5253      +/-   ##
==========================================
+ Coverage   70.33%   72.37%   +2.03%     
==========================================
  Files         238      238              
  Lines       14013    14640     +627     
  Branches      543      599      +56     
==========================================
+ Hits         9856    10595     +739     
+ Misses       4157     4045     -112     

Impacted Files	Coverage Δ
...penwhisk/core/containerpool/ContainerFactory.scala	89.47% <100.00%> (+0.58%)	⬆️
...ontainerpool/v2/FunctionPullingContainerPool.scala	82.65% <100.00%> (+1.66%)	⬆️
...core/database/cosmosdb/RxObservableImplicits.scala	0.00% <0.00%> (-100.00%)	⬇️
...ore/database/cosmosdb/cache/CacheInvalidator.scala	0.00% <0.00%> (-100.00%)	⬇️
...e/database/cosmosdb/cache/ChangeFeedConsumer.scala	0.00% <0.00%> (-100.00%)	⬇️
...core/database/cosmosdb/CosmosDBArtifactStore.scala	0.00% <0.00%> (-95.85%)	⬇️
...sk/core/database/cosmosdb/CosmosDBViewMapper.scala	0.00% <0.00%> (-93.90%)	⬇️
...tabase/cosmosdb/cache/CacheInvalidatorConfig.scala	0.00% <0.00%> (-92.31%)	⬇️
...enwhisk/connector/kafka/KamonMetricsReporter.scala	0.00% <0.00%> (-83.34%)	⬇️
...e/database/cosmosdb/cache/KafkaEventProducer.scala	0.00% <0.00%> (-78.58%)	⬇️
... and 49 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0c4aab1...daf7c53. Read the comment docs.

[ningyougang]

LGTM