[YUNIKORN-2319] cache.Task: reference to old pod object is kept after update

[pbacsko]

What is this PR for?

Whenever a pod is updated, then replace it inside the Task as well so that the previous version can be garbage collected.

What type of PR is it?

• - Bug Fix
• - Improvement
• - Feature
• - Documentation
• - Hot Fix
• - Refactoring

Todos

• - Task

What is the Jira issue?

https://issues.apache.org/jira/browse/YUNIKORN-2319

How should this be tested?

Screenshots (if appropriate)

Questions:

• - The licenses files need update.
• - There is breaking changes for older versions.
• - It needs documentation.

[codecov]

Codecov Report

Attention: Patch coverage is 94.73684% with 1 line in your changes missing coverage. Please review.

Project coverage is 67.43%. Comparing base (18c9985) to head (f2e5798).

Files	Patch %	Lines
pkg/cache/context.go	91.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #864      +/-   ##
==========================================
+ Coverage   67.38%   67.43%   +0.04%     
==========================================
  Files          70       70              
  Lines        7623     7633      +10     
==========================================
+ Hits         5137     5147      +10     
  Misses       2268     2268              
  Partials      218      218              

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[pbacsko]

@wilfred-s could you review this chage?

[craigcondit]

+1 LGTM.