test: Make some stratis tests nondestructive

[martinpitt]

test{Basic,Alerts,Cli} don't reboot and thus can run in our nondestructive VMs and on the Testing Farm. Move the others into a new TestStorageStratisReboot test class (that way around, the pixel tests have a lot less renaming noise). Change them to use loop devices, and ensure that failed tests clean up after themselves by stopping+destroying all leftover pools and creating mount points in vm_tmpdir.

This paves the way for doing reverse dependency testing for stratis changes.

https://issues.redhat.com/browse/COCKPIT-1070

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There's unfortunately some pixel noise, as the dialog previously had the "QEMU ..." name, and now with the loop devices they don't have a serial/label; and there's one rename.

[martinpitt]

Hmm, I could avoid some pixel noise by keeping TestStorageStratis as-is, and renaming the other class to TestStorageStratisReboot

Update: Done.

[martinpitt]

Works on our CI now, but still fails on TF. Missing stratis dependency at least.

[martinpitt]

This is a "fun" failure. There is some leaked /dev/loop12 (possibly from TestStoragePartitions.testPartitions? -- no, it's not, the test would fail earlier otherwise), and that makes .sidepanel-row:contains(/dev/loop1)" ambiguous. Unfortunately the sidebar doesn't have an attribute with the precise device name.

Update: This debug log shows that it's not a leak, it's just that losetup decides to actually allocate these names:

XXXX testBasic loop assignment /dev/loop0 /dev/loop12 /dev/loop1 /dev/loop2 /dev/loop3

I'll try to fix them.

[mvollmer]

Unfortunately the sidebar doesn't have an attribute with the precise device name.

The redesign will fix this! :-)

[mvollmer]

Thanks!