[2132793] Edited Template BSR is not saved

Description of problem: When editing boot source rererence of Template, the changes are not saved

Version-Release number of selected component (if applicable): v4.12.0-131

How reproducible: always

Steps to Reproduce:
1. Select Template without source, e.g. windows11-desktop-large
2. Select Edit boot source reference from Actions menu
3. Provide boot reference, e.g. Registry/quay.io/containerdisks/centos:7-2009 or URL/http://cnv-qe-server.rhevdev.lab.eng.rdu2.redhat.com/files/cnv-tests/cirros-images/cirros-0.5.1-x86_64-disk.img
4. Save
5. Select Edit boot source reference from Actions menu again

Actual results: Changes are not saved

Expected results: Changes are saved, Template has "Source available" label in Templates list and Catalog

Additional info: related problem in 4.11: https://bugzilla.redhat.com/show_bug.cgi?id=2106179