fix(tasks): correct mount audit logic and variable naming in section 1

[teebee]

Overall Review of Changes:
This PR corrects critical logical errors and variable naming inconsistencies in the partition audit tasks of Section 1 (Benchmarks 1.1.2.1.x through 1.1.2.7.x).

1. Variable naming: Fixed copy-paste errors where tasks for /home and /var incorrectly referenced discovered_dev_shm_mount instead of their own registered variables.
2. Logic fix: Changed the check from is undefined to .rc != 0. Since the preceding command task uses register, the variable is always defined, which previously caused the audit warnings to be skipped entirely.

Issue Fixes:
N/A (Found during manual code review and verified via testing)

Enhancements:

• Improved reliability of the audit summary by ensuring that missing partitions are correctly detected and added to the warn_control_list.
• Standardized the audit check pattern across all mount-related tasks in Section 1.

How has this been tested?:
Verified using a dedicated test playbook on an Ubuntu 22.04 VM.

• Scenario A (Missing partition): Confirmed that findmnt returns RC 1, and the new .rc != 0 logic correctly triggers the warning and includes it in the warning_facts summary.
• Scenario B (Existing partition): Confirmed that the task is skipped as expected when .rc == 0.

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