test: rptests tests running on Azure can't use rp-storage-tool

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Version & Environment

Redpanda version: Nightly on 7/7/2023 CDT Tests on Azure: https://buildkite.com/redpanda/vtools/builds/8757#0189d175-1058-4635-bce4-be32aa14a429

What went wrong?

rp-storage-tool can't find required attribute

    AttributeError("'NoneType' object has no attribute 'conn_str'")
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/dist-packages/ducktape/tests/runner_client.py", line 135, in run
    data = self.run_test()
  File "/usr/local/lib/python3.10/dist-packages/ducktape/tests/runner_client.py", line 227, in run_test
    return self.test_context.function(self.test)
  File "/home/ubuntu/redpanda/tests/rptest/services/cluster.py", line 159, in wrapped
    self.redpanda.stop_and_scrub_object_storage()
  File "/home/ubuntu/redpanda/tests/rptest/services/redpanda.py", line 4082, in stop_and_scrub_object_storage
    report = self._get_object_storage_report(timeout=run_timeout)
  File "/home/ubuntu/redpanda/tests/rptest/services/redpanda.py", line 3976, in _get_object_storage_report
    "AZURE_STORAGE_CONNECTION_STRING"] = self.cloud_storage_client.conn_str
AttributeError: 'NoneType' object has no attribute 'conn_str'

How to reproduce the issue?

1. Use following env variables no Buildkite to run CDT on Azure using vtools Group

   ENABLE_STEP_CDT=1
   CDT_CLOUD_REGION=Central US
   CDT_CLOUD_PROVIDER=azure
   DISABLE_STEP_K8S_OPERATOR=1
   REDPANDA_CDT_INSTANCE_TYPE=Standard_L8s_v3
   DISABLE_STEP_CHAOS_REDPANDA=1
   DISABLE_STEP_MULTIARCH_IMAGE=1
   DISABLE_STEP_TEST_CLANG_AMD64=1
   DISABLE_STEP_TEST_CLANG_ARM64=1
   DISABLE_STEP_DEBUG_CLANG_AMD64=1
   DISABLE_STEP_K8S_UNSTABLE_TESTS=1
   DISABLE_STEP_RELEASE_CLANG_AMD64=1

JIRA Link: CORE-1390

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Tracking issue in core-internal: https://github.com/redpanda-data/core-internal/issues/727