[YUNIKORN-2845] Remove SchedulerConf.TestMode

[pbacsko]

What is this PR for?

Remove SchedulerConf.TestMode because it's no longer needed.

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-2845

How should this be tested?

Screenshots (if appropriate)

Questions:

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

[craigcondit]

+1 LGTM, pending rebase and tests passing.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 68.28%. Comparing base (4d6b4de) to head (1612d8c).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #923      +/-   ##
==========================================
+ Coverage   68.21%   68.28%   +0.06%     
==========================================
  Files          70       70              
  Lines        7621     7611      -10     
==========================================
- Hits         5199     5197       -2     
+ Misses       2214     2205       -9     
- Partials      208      209       +1     

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