Comment 21 for bug 1576989

All the fixes we had picked for https://bileto.ubuntu.com/#/ticket/1411 for backporting 5.4 are in 5.5 and 5.6, but we didn't and don't have a good test case to prove if they fix our problems or not.

For reference, the patches we tried to pick but decided not to land for potential risks were:
QLockFile-Avoid-zero-sized-lock-file-on-write-error.patch
QLockFile-fix-deadlock-when-the-lock-file-is-corrupt.patch
QLockFile-sync-to-disk-to-avoid-leaving-an-empty-loc.patch

They do sound like they should be fixing at least part of the problems, and there were one or two more still in the 5.5/5.6 branches to the related files.