NAS-127298 / 25.04 / Add extensive iSCSI ALUA unit test

[bmeagherix]

Add a more extensive iSCSI ALUA test.

• Test that an ALUA target - without a LUN 0 - works correctly with only LUN 100. The previous test_33_no_lun_zero tests purely from client perspective, but this new test (test_alua_lun_100) will also exercise the "internal" target used in ALUA.
• Test a non-trivial ALUA configuration. This includes targets with no LUNs, one LUN, two LUNs & five LUNs - 10 targets, 16 LUNs in total. With this config ...
• Use KVM virsh command to power off the current ACTIVE node (i.e. not a clean shutdown) and ensure that the previous STANDBY node serves the ALUA targets, as soon as failover is complete.
• Reset the current ACTIVE, and repower the previous ACTIVE and ensure that ALUA targets are served by both nodes. (Clean simultaneous boot of both nodes.)
• Finally, if necessary reboot the ACTIVE so that the original ACTIVE node is restored. (i.e. clean reboot)

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Clean CI run (wrt iSCSI) here.

[bugclerk]

Jira URL: https://ixsystems.atlassian.net/browse/NAS-127298

[bugclerk]

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