fix #4924: handles non-okhttp clients with invalid watch status

[shawkins]

Description

In trying to run the other clients against the kubernetes-tests, WatchTest had a failure - responding with 200, null was actually providing the literal "null" result. This is not seen by the okhttp logic because it doesn't provide the response to websocket request exceptions, but we do for the other client types. Treating this as a status creates a null value and ensuing NPE - but that is swallowed by the current exception handling. These changes make everything appropriately defensive.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change
• Chore (non-breaking change which doesn't affect codebase;
  test, version modification, documentation, etc.)

Checklist

• Code contributed by me aligns with current project license: Apache 2.0
• I Added CHANGELOG entry regarding this change
• I have implemented unit tests to cover my changes
• I have added/updated the javadocs and other documentation accordingly
• No new bugs, code smells, etc. in SonarCloud report
• I tested my code in Kubernetes
• I tested my code in OpenShift

[sonarqubecloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
2 Code Smells

57.1% Coverage
0.0% Duplication