tests: fix TestNodeSetCatchpointCatchupMode data race

[algorandskiy]

Summary

Fixed a data race as seen here:

WARNING: DATA RACE
Write at 0x00c02383dea8 by goroutine 12204:
  runtime.racewrite()
      <autogenerated>:1 +0x1e
  github.com/algorand/go-algorand/node.(*AlgorandFullNode).waitMonitoringRoutines()
      /home/runner/work/go-algorand/go-algorand/node/node.go:470 +0x1db
  github.com/algorand/go-algorand/node.(*AlgorandFullNode).SetCatchpointCatchupMode.func1.1()
      /home/runner/work/go-algorand/go-algorand/node/node.go:1269 +0x4e
  runtime.deferreturn()
      /opt/hostedtoolcache/go/1.25.3/x64/src/runtime/panic.go:589 +0x5d

Previous read at 0x00c02383dea8 by goroutine 12232:
  runtime.raceread()
      <autogenerated>:1 +0x1e
  github.com/algorand/go-algorand/node.(*AlgorandFullNode).startMonitoringRoutines()
      /home/runner/work/go-algorand/go-algorand/node/node.go:454 +0x94
  github.com/algorand/go-algorand/node.(*AlgorandFullNode).SetCatchpointCatchupMode.func1()
      /home/runner/work/go-algorand/go-algorand/node/node.go:1307 +0x7d1

What happens is enable=true call stops goroutines but unblocks the caller waiting on <-outCh earlier then it actually completes, allowing the caller to call SetCatchpointCatchupMode. Rarely it these two goroutines race on WaitGroup's Add and Wait methods.

Test Plan

Run locally go test ./node -race -run TestNodeSetCatchpointCatchupMode -count=100 (same as before the fix, no repro).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 47.82%. Comparing base (8d84b18) to head (4c1083f).
⚠️ Report is 4 commits behind head on master.
✅ All tests successful. No failed tests found.

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HEAD has 4 uploads less than BASE

Flag	BASE (8d84b18)	HEAD (4c1083f)
full_coverage	4	0

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #6574       +/-   ##
===========================================
- Coverage   63.60%   47.82%   -15.78%     
===========================================
  Files         486      646      +160     
  Lines       67806    89431    +21625     
===========================================
- Hits        43125    42767      -358     
- Misses      21188    43852    +22664     
+ Partials     3493     2812      -681     

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