fix incorrect handling of NEW_RELIC_MYSQL_ROOT_PASSWORD

[keita-mitsuhashi]

Issue:
The playbook incorrectly outputs the literal string "item.NEW_RELIC_MYSQL_ROOT_PASSWORD" instead of the actual value of the environment variable.

Fix:
Updated the playbook to ensure proper variable interpolation. Changes include:

• Correctly wrapping NEW_RELIC_MYSQL_ROOT_PASSWORD in {{ }} in the set_fact task.
• Ensuring the debug task displays the actual value of mysql_root_password.

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[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}