Update CosmosDB to 2.4.2

[chetanmeh]

Updates CosmosDB to 2.4.2 (from 2.4.0) as it has some fixes related to cross partition queries

Description

Couple of changes in this PR

1. Update to CosmosDB SDK 2.4.2
2. Removes support for storing attachment in ComsosDB and requires an external AttachmentStore to be configured. (Fixes Storing attachments in CosmosDB fails with v2.4.0 #4286)
3. Reduces the configured throughput for test runs to 400 from current 1000. Would save some money!

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
• 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 #4321 into master will decrease coverage by 4.32%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #4321      +/-   ##
==========================================
- Coverage   85.71%   81.39%   -4.33%     
==========================================
  Files         168      168              
  Lines        7870     7814      -56     
  Branches      524      520       -4     
==========================================
- Hits         6746     6360     -386     
- Misses       1124     1454     +330

Impacted Files	Coverage Δ
...core/database/cosmosdb/CosmosDBArtifactStore.scala	0% <0%> (-95.11%)	⬇️
...core/database/cosmosdb/RxObservableImplicits.scala	0% <0%> (-100%)	⬇️
...sk/core/database/cosmosdb/CosmosDBViewMapper.scala	0% <0%> (-92.6%)	⬇️
...whisk/core/database/cosmosdb/CosmosDBSupport.scala	0% <0%> (-84.62%)	⬇️
...abase/cosmosdb/CosmosDBArtifactStoreProvider.scala	4% <0%> (-52%)	⬇️
...in/scala/org/apache/openwhisk/common/Counter.scala	40% <0%> (-20%)	⬇️
.../scala/org/apache/openwhisk/utils/Exceptions.scala	20% <0%> (-20%)	⬇️
...whisk/connector/kafka/KafkaProducerConnector.scala	72.5% <0%> (-15%)	⬇️
...nwhisk/core/database/cosmosdb/CosmosDBConfig.scala	94.11% <0%> (-5.89%)	⬇️
... and 1 more

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[chetanmeh]

Travis build for branch passed which has CosmosDB test enabled

[tysonnorris]

LGTM Thanks!