qemu-img convert makes a number of allocation requests, and less
common than the "Resource temporarily unavailable" error is
"Cannot allocate memory". The first seems to be largely raised
upon a thread creation for the image conversion, where the first
appears to be on buffer setup on the original process.
Regardless, we should check for both and retry conversion
automatically.
rhbz# 1892773
Note: Because of a later patch which transformed the retry logic to
leverage tenacity, this change has been modified accordingly.
Change-Id: If435ed0efe034d4bb99f0281ebc73840c0f38fb3
(cherry picked from commit 9be6afc751)
(cherry picked from commit 9790280301)
000ea74d34