Log data migration script output when script failed

[Bin Qian]

this is an enhancement for logging stdout/stderr from data migration scripts on failure, especially for shell scripts. error output could be the best debug info to indicate the failure.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/starlingx/config/+/857934

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/starlingx/config/+/857934
Committed: https://opendev.org/starlingx/config/commit/b6cc163bc617c8d41b090268b5f0abc9ac114d9e
Submitter: "Zuul (22348)"
Branch: master

commit b6cc163bc617c8d41b090268b5f0abc9ac114d9e
Author: Bin Qian <email address hidden>
Date: Thu Sep 15 14:41:54 2022 +0000

    Log data migration script output when failure

    Capture script stdout and stderr. Log outputs when script fails.
    Do not log exception unless script cannot run.

    Closes-bug: 1989742

    TCs:
        1. No log for execution succeed
        2. script output is logged when script fails
        3. exception is logged when script not executed (e.g, file not
           found, etc)

    Signed-off-by: Bin Qian <email address hidden>
    Change-Id: I9c5e01e0937db02624f8c4b9bff5ccb2fae73249