DAOS-16334 test: Fix permission denied removing temporary test files (#15022)

[phender]

Update the --control-metadata-path assignment for dmg config generate command to avoid issues cleaning up the files generated.

Skip-unit-tests: true
Skip-fault-injection-test: true
Skip-func-hw-test-large-md-on-ssd: false

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[github-actions]

Ticket title is 'control/config_generate_run.py:ConfigGenerateRun.test_config_generate_run - Permission denied removing temporary test files'
Status is 'Awaiting backport'
Labels: 'ci_master_weekly,request_for_2.6.1,scrubbed_2.8,weekly_test'
https://daosio.atlassian.net/browse/DAOS-16334