tests: mask iscsi service to avoid intermittent errors on github runners #2453

Job	Run time
Check secrets / Check secret	1s
Packaging (xenial)	4m 16s
Packaging (bionic)	6m 15s
Packaging (focal)	4m 1s
Packaging (jammy)	3m 40s
Packaging (lunar)	3m 35s
Packaging (mantic)	3m 47s
Integration (bionic, lxd, ubuntu-22.04)	1h 4m 34s
Integration (focal, lxd, ubuntu-22.04)	1h 38m 31s
Integration (jammy, lxd, ubuntu-22.04)	51m 47s
Integration (lunar, lxd, ubuntu-22.04)	28m 6s
Integration (xenial, lxd, ubuntu-20.04)	1h 26m 9s
Integration (bionic, awspro, ubuntu-22.04)	36m 57s
Integration (bionic, gcppro, ubuntu-22.04)	44m 23s
Integration (bionic, awspro-fips, ubuntu-22.04)	16m 2s
	7h 32m 4s

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