Add /dev/disk/by-id link tests

[hamistao]

This adds tests for checking if /dev/disk/by-id links are being properly set up for different kinds of block devices. Also moves non pool specific tests away from storage-vm.
This is needed for #13672 and #13671.

[tomponline]

There seems to be some commits that are iterating on changes of the same lines - please dont do this. As discussed before each line change should be the final version of a logical change - not an iteration.

Secondly, we agreed on Friday that we would move the "Checking additional disk device support" tests from storage-vm to storage-disks-vm so as to keep the external disks together in one file and so as to avoid repeating them for each pool driver unnecessarily, however I do not see this change.

[tomponline]

@hamistao additionally please can you also add some tests to the storage-disks-vm file that checks for devices passed with long & escaped names that are longer than what udev uses, so we can check the udev /dev/disk/by-id path is unchanged. Ta

[hamistao]

@tomponline I am planning to include the discussed moving of the tests on a later PR along with other similar changes to make this simpler.
Also, using long names don't serve a lot of purpose here because the name is trimmed to about 16 characters when added to the /dev/disk/by-id path (e.g.: device-with-very-long-name becomes scsi-0QEMU_QEMU_HARDDISK_lxd_device--with--ve), if you think it still makes sense to use them I can make the changes. As for escaped names, I believe I am using one here.

Edit: Sorry I misread your message, the purpose is to go beyond the limit on udev. I am afraid this may break the tests, I am doing some investigation and will open an issue on this shortly

[hamistao]

@tomponline The new long name tests were added, feel free to take a look at this when you can. The tests seem to be failing due to unrelated problems with latest/edge.

[tomponline]

Thanks, unfortunately as latest/edge is now broken ill hold off on this until @mihalicyn and I can unblock it.

[tomponline]

The new long name tests were added

You mentioned some devices didn't work with long names - please can you elaborate on this.

[hamistao]

@tomponline It seemed like using long names could break the devices but in fact, the paths on /dev/ and /dev/disk/by-id behave differently. For example, on ubuntu-minimal VMs adding two devices with names that share a 16 character prefix, the /dev/disk/by-id path of the first would be overwritten by the second, leaving the first without a link on /dev/disk/by-id.
For the purpose of these tests, thay are not affected by this behavior.

[hamistao]

Thanks, unfortunately as latest/edge is now broken ill hold off on this until @mihalicyn and I can unblock it.

No problem!

[hamistao]

@tomponline I will push new changes removing the tests that use readlink to check links to /dev/sd*, as was discussed earlier with @simondeziel

[tomponline]

Good news, the latest/edge is unblocked and the tests are green.

Just need to understand about the restrictions being relaxed and then we can merge.

[simondeziel]

Please remove remaining traces of /dev/sdX everywhere.

[hamistao]

@tomponline This is ready for another look

[tomponline]

Thanks!

changes made