vmm_tests: investigate intermittent failure with validating mnf usage within guests

[damanm24]

Investigate this specific flavor of vmm_test: openvmm_openhcl_uefi_x64 to find root cause of flakiness. See the following logs from a failed run: https://openvmm.dev/test-results/test.html?run=18293739153&job=x64-windows-intel-vmm-tests-logs&test=multiarch__vmbus_relay__openvmm_openhcl_uefi_x64_ubuntu_2204_server_x64_validate_mnf_usage_in_guest