QCOW2 files will be used to store the VM's data on ChromeOS. Add
support for basic reading and writing of qcow files.
CQ-DEPEND=CL:872451
BUG=none
TEST=qcow unit tests and use "qemu-image check" to verify generated qcow
files.
Change-Id: I4b9e77e58edca69f894ede19e79ebd2cd7b2623e
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/862628
Reviewed-by: Stephen Barber <smbarber@chromium.org>
