[Test] Stabilize bootstrap of proxy instance used for testing and facilitate troubleshooting

[gmarciani]

Description of changes

Improvement to the bootstrap of proxy infra used for testing:

1. stabilized bootstrap by preventing failure caused by dpkg locking
2. facilitate troubleshooting by surfacing the broken instance id in the failure message reported by the test.

Tests

Executed the following tests, which all succeeded the bootstrap of the proxy infrastructure.

test-suites:
  createami:
    test_createami.py::test_build_image_no_internet:
      dimensions:
        # RHEL family (rhel8, rhel9) -> Red Hat Enterprise Linux reservation platform
        - regions: [{{ g4dn_2xlarge_CAPACITY_RESERVATION_2_INSTANCES_3_HOURS_NOPG_rhel9 }}]
          instances: ["g4dn.2xlarge"]
          oss: ["rhel8", "rhel9"]
        # Non-RHEL family (alinux2023, ubuntu2204, ubuntu2404, rocky8, rocky9) -> Linux/UNIX reservation platform
        - regions: [{{ g4dn_2xlarge_CAPACITY_RESERVATION_5_INSTANCES_3_HOURS_NOPG_ubuntu2404 }}]
          instances: ["g4dn.2xlarge"]
          oss: ["alinux2023", "ubuntu2204", "ubuntu2404", "rocky8", "rocky9"]

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.