qemu-img fixed vhd issues

[Lucian Petrut]

qemu-img returns fixed vhd images file format to be raw.

This happens because only the header is seeked for image signatures when getting the image format. In fact, unlike dynamic vhd images, differencing vhds don't have the footer copied in the header.

An easy fix would be to just search the last 512B for the 'conectix' signature.

Also, the fixed vhds created by qemu-img seem to be corrupted from Powershell POV.

[Thomas Huth (th-huth)]

Triaging old bug tickets... can you still reproduce this issue with the latest version of QEMU? Or could we close this ticket nowadays? Otherwise, can you provide some test images or a description how to create such images?

[Zixuan Wang (the.netadmin)]

Yes I can reproduce this issue on Windows 10 with newest version of QEMU (until 03/28/2018)

I've posted my way of reproduce in a new bug issue:
`#1759522 windows qemu-img create vpc/vhdx error`

[Zixuan Wang (the.netadmin)]

Sorry for the mistaken operation (changed to confirmed), I didn't mean to change the status

[Thomas Huth (th-huth)]

This is an automated cleanup. This bug report has been moved to QEMU's
new bug tracker on gitlab.com and thus gets marked as 'expired' now.
Please continue with the discussion here:

 https://gitlab.com/qemu-project/qemu/-/issues/107