If the download URL for an icon was already cached locally, the HTTP
code returned FLATPAK_OCI_ERROR_NOT_CHANGED - this was treated as a real
error, and after downloading missing icons, all present icons were
deleted!
See https://bugzilla.redhat.com/show_bug.cgi?id=1683375Closes: #3048
Approved by: alexlarsson
(cherry picked from commit a794c07e18)
(cherry picked from commit 767a9d5a43)
Closes: #3115
Approved by: alexlarsson