The chunk size used for downloading images was 64KiB for some time. That
is okay for relatively small images but the client side of CPU can be a
bottleneck especially for large images. Bump the default chunk size from
64KiB to 1MiB so we can use the client side CPU more efficiently.
[64KiB chunk size - current]
INFO cinder.image.image_utils Image download 1907.35 MB at 68.61 MB/s
-> ~ 549 Mbps
[1MiB chunk size - patched]
INFO cinder.image.image_utils Image download 1907.35 MB at 132.10 MB/s
-> 1,057 Mbps
Closes-Bug: #2020139
Change-Id: I8b6e19621fc989526b02319d88fcfde88a17eee0
(cherry picked from commit 7d78cc4b9d)
3a2ef8b105