test: use `my_curl()` helper where applicable #10269

Job	Run time
Documentation	4m 7s
Code	9m 5s
Client (1.22.x, ubuntu-latest)	23s
Client (1.22.x, macos-latest)	23s
System (1.22.x, cluster, dir)	12m 42s
Client (1.22.x, windows-latest)	2m 2s
System (1.22.x, cluster, btrfs)	13m 12s
System (1.22.x, cluster, lvm)	13m 6s
System (1.22.x, cluster, zfs)	15m 47s
System (1.22.x, cluster, ceph)	16m 16s
System (1.22.x, cluster, random)	12m 38s
System (1.22.x, standalone, dir)	25m 37s
System (1.22.x, standalone, btrfs)	25m 0s
System (1.22.x, standalone, lvm)	44m 3s
System (1.22.x, standalone, zfs)	42m 18s
System (1.22.x, standalone, ceph)	1h 21m 8s
System (1.22.x, standalone, random)	38m 30s
System (stable, cluster, dir)	11m 55s
System (stable, standalone, dir)	24m 13s
Trigger snap edge build	0s
	6h 32m 25s

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