PMM-13431 Fix long tmp directory names in pmm-agent

[ademidoff]

Ticket number: PMM-13431

Feature build: SUBMODULES-4392

Tests: percona/pmm-qa#997

[codecov]

Codecov Report

❌ Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 43.52%. Comparing base (16ac903) to head (ddee0b6).

Files with missing lines	Patch %	Lines
agent/agents/supervisor/supervisor.go	75.00%	1 Missing ⚠️
agent/commands/run.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##               v3    #5459      +/-   ##
==========================================
- Coverage   43.54%   43.52%   -0.02%     
==========================================
  Files         413      413              
  Lines       42928    41858    -1070     
==========================================
- Hits        18692    18220     -472     
+ Misses      22363    21998     -365     
+ Partials     1873     1640     -233     

Flag	Coverage Δ
agent	49.15% <60.00%> (ø)

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