+++ This bug was initially created as a clone of Bug #2017432 +++
This bug was cloned to address remaining flaws not fixed in the original one. The remaining issues are that when using several multipath devices (and some of them deselected) with custom partitioning, then:
- total disk capacity is wrong
- total disk count available for partitioning is wrong (selected mpath devices + all of the underlying devices)
- the list of disks available for partitioning is wrong (selected mpath devices + all of the underlying devices)

Reproducer:
1. Create a VM with 4 raw disk images, each of them connected as two SCSI/SATA drives with image sharing enabled and the same serial number for each pair (I used 0001-0004).
2. Start system installation and proceed to partitioning spoke.
3. Click on 'Add a disk button', select all of the mpathX devices and confirm the selection.
4. Deselect first two drives (e. g. mpatha, mpathb).
5. Select custom partitioning and proceed into the custom partitioning spoke.
6a. Check the amount of 'Total space'.
6b. Check the number of 'Selected storage devices' in the bottom part of the screen.
6c. Click on the 'X storage drives selected' link and check the list of available drives.

Actual results:
6a. The total disk space reported is wrong and accounts for a sum of the selected mpath devices (e. g. mpathc, mpathd) plus the underlying devices (e. g. sda, sdb, sdc, sdd).
6b. The number of selected storage devices is wrong (sum of the mpath devices plus the underlying devices, i. e. 6 instead of 2).
6c. The list of selected devices is wrong, i. e. contains both the mpath devices AND the underlying devices.

Expected results:
6a. The total disk space is just a sum of the mpath disks selected for partitioning in step 4.
6b. The number of selected drives is based only on the count of mpath disks selected for partitioning (not the underlying devices of the mpath disks).
6c. The list only contains the mpath disks, not the underlying devices.


* Here's a copy of the pre-verification comment from bug 2017432 just in case some more details could be useful:

Reproduced on RHEL-9.0.0-20220117.0 x86_64 / python3-blivet-3.4.0-11.el9 using a VM with 8 disks (using 10 GB and 3x 1 GB images, every image connected as two disks with identic serial numbers), resulting in 4 mpath devices:
- anaconda let me properly add all of the devices for partitioning (mpatha-mpathd)
- I could select just two of them (mpathc, mpathd) to be used for partitioning/installation
- in custom partitioning, the available space was reported properly (11 GiB = 10 + 1 GiB), but at the same time the total space value was incorrect (33 GiB = 10 GiB sda + 10 GiB sdb + 2*1 GiB sdc/sdd + 10 GiB mpathc + 1 GiB mpathd)
- the number of available storage devices was incorrect - 6 (should be 4), the list consisted of mpathc, mpathd, sda, sdb, sdc, sdd
- when I tried to create /boot partition, it resulted in an error and showing the details just resulted in a window with '/dev/sda'

Pre-verification on RHEL-9.0.0-20220209.d.0 / python3-blivet-3.4.0-12.el9 using the same setup was successful in the main point (partitioning), but still not flawless:
- anaconda let me properly add all of the devices for partitioning (mpatha-mpathd)
- I could select just two of them (mpathc, mpathd) to be used for partitioning/installation
- the available space was again reported correctly, but at the same time the total space was incorrect again (33 GiB)
- the number of available storage devices was still incorrect (6)
- the important change is that I was able to create partitioning and successfully finish the installation + boot the system.