e2e test wait for grpc server teardown and stop agents

[6543]

fix race of https://ci.woodpecker-ci.org/repos/3780/pipeline/33699/39

we also now stop agents gracefully

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 41.11%. Comparing base (8e6084c) to head (a12fb48).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6479      +/-   ##
==========================================
- Coverage   41.25%   41.11%   -0.15%     
==========================================
  Files         431      431              
  Lines       28792    28791       -1     
==========================================
- Hits        11878    11836      -42     
- Misses      15847    15892      +45     
+ Partials     1067     1063       -4     

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