Fix a logic bug in the notification hook

[DrChat]

Summary of the Pull Request

This PR fixes a simple logic error in the notification hook, which caused it to return an error response if the Teams endpoint succeeded.
In addition, this changes the code to return proper HTTP error codes if the script fails.

PR Checklist

• Applies to work item: #xxx
• CLA signed. If not, go over here and sign the CLI.
• Tests added/passed
• Requires documentation to be updated
• I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

[codecov-commenter]

Codecov Report

Merging #2627 (ad619d5) into main (07befc5) will increase coverage by 1.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2627      +/-   ##
==========================================
+ Coverage   29.37%   30.37%   +1.00%     
==========================================
  Files         290      255      -35     
  Lines       35596    29440    -6156     
==========================================
- Hits        10455     8942    -1513     
+ Misses      25141    20498    -4643     

Impacted Files	Coverage Δ
src/agent/coverage/src/test.rs	92.85% <0.00%> (-7.15%)	⬇️
src/agent/coverage/src/code.rs	8.29% <0.00%> (-6.12%)	⬇️
src/agent/onefuzz/src/machine_id.rs	51.21% <0.00%> (-5.63%)	⬇️
src/agent/onefuzz/src/sanitizer.rs	69.69% <0.00%> (-2.91%)	⬇️
src/agent/onefuzz-agent/src/worker/tests.rs	99.10% <0.00%> (-0.11%)	⬇️
src/agent/onefuzz/src/asan.rs	0.00% <0.00%> (ø)
src/agent/coverage/src/cache.rs	0.00% <0.00%> (ø)
src/agent/onefuzz-agent/src/setup.rs	0.00% <0.00%> (ø)
src/agent/onefuzz-agent/src/reboot.rs	0.00% <0.00%> (ø)
src/agent/onefuzz/src/input_tester.rs	0.00% <0.00%> (ø)
... and 47 more

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