fix action not processing metric

[bdoyle0182]

Description

Since the metric is a gauge, it will continue reporting the value once an action starts not processing and will never recover from the metric's perspective even if the action has actually recovered. Setting the gauge back to 0 should handle recovery without requiring a restart.

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 #5395 (70162e3) into master (cb3b64f) will decrease coverage by 11.32%.
The diff coverage is 0.00%.

❗ Current head 70162e3 differs from pull request most recent head e9f29cd. Consider uploading reports for the commit e9f29cd to get more accurate results

@@             Coverage Diff             @@
##           master    #5395       +/-   ##
===========================================
- Coverage   76.87%   65.55%   -11.32%     
===========================================
  Files         240      240               
  Lines       14597    14600        +3     
  Branches      620      634       +14     
===========================================
- Hits        11221     9571     -1650     
- Misses       3376     5029     +1653     

Impacted Files	Coverage Δ
...e/openwhisk/core/scheduler/queue/MemoryQueue.scala	0.00% <0.00%> (-82.36%)	⬇️

... and 56 files with indirect coverage changes

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[style95]

LGTM