Add timeout to apt update to prevent indefinite hang on network issues

[dassayantan24]

Context

Self-hosted VMSS agents on Linux hang indefinitely during startup when external Ubuntu repos are unreachable. The installdependencies.sh script runs apt update with no timeout — if the network silently drops packets, the agent never becomes healthy and pipeline jobs are stuck until manual intervention

AB#2393470

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Description

#5553

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Risk Assessment (Low / Medium / High)

Low

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Unit Tests Added or Updated (Yes / No)

No

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Additional Testing Performed

• Manually tested on Linux self-hosted agent where the below command exited with a 2-minute timeout

 docker run --rm -v "$(pwd)/src/Misc/layoutbin:/agent-bin" ubuntu:24.04 \
   bash -c "
     echo 'deb http://192.0.2.1/ubuntu noble main' > /etc/apt/sources.list
     rm -rf /etc/apt/sources.list.d/*
     echo 'Starting at:' && date
     bash /agent-bin/installdependencies.sh
     echo 'Finished at:' && date
     echo 'Exit code:' \$?
   "

• Additionally, I tested the self-hosted agent on regular pipelines as well.

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Change Behind Feature Flag (Yes / No)

No

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Tech Design / Approach

• Design has been written and reviewed.
• Any architectural decisions, trade-offs, and alternatives are captured.

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Documentation Changes Required (Yes/No)

Indicate whether related documentation needs to be updated.

• User guides, API specs, system diagrams, or runbooks are updated.

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Logging Added/Updated (Yes/No)

• Appropriate log statements are added with meaningful messages.
• Logging does not expose sensitive data.
• Log levels are used correctly (e.g., info, warn, error).

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Telemetry Added/Updated (Yes/No)

• Custom telemetry (e.g., counters, timers, error tracking) is added as needed.
• Events are tagged with proper metadata for filtering and analysis.
• Telemetry is validated in staging or test environments.

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Rollback Scenario and Process (Yes/No)

• Rollback plan is documented.

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Dependency Impact Assessed and Regression Tested (Yes/No)

• All impacted internal modules, APIs, services, and third-party libraries are analyzed.
• Results are reviewed and confirmed to not break existing functionality.