Bug 1023402

Description of problem:
When revisiting "Installation destination" the free space displayed for each disk is Free space minus to-be-created volumes.

It may be reasonable to show "used for this install" sizes as well.

What's worse, once I click "Done" and there is not enough free space for _whole installation_ the "Installation options" shows Free space without already pre-allocated space and says "You don't have enough space available to install Fedora" even though the only missing part is /boot partition and I already have / and swap allocated.

Version-Release number of selected component (if applicable):
20.25.1-1

How reproducible:
100%

Steps to Reproduce:
1. select thin-provisioning layout and custom partitioning
2. ask anaconda to create default partitions for you
3. remove /boot
4. confirm
5. Main hub correctly reports there is an error
6. Go to "Installation destination" and select Done

Actual results:
The "Installation option" dialog claiming there is not enough space will appear.
One may be tempted to enter "Reclaim space" here [1]

Expected results:
The normal "Installation option" dialog should be present.

Additional info:

[1] NOTE: Which BTW allows reclaiming part of about to create fedora VG, which is then incomplete and is displayed as Unknown and is IMO Bug too. And it is displayed as lvmpv when there is PV not in a VG, PV in a VG directly on disk without partition or not all disks are selected - this may result in wrong disks being selected for installation and is Bug too. And it is missing an option to delete particular LVs. And the free space in existing VGs and pools is not taken into account. Those creatures are breeding exponentially!