guest-fsfreeze can't work well on windows
Description of problem:
I used qemu 5.0 to cross-compile windows gqa on the fedroa30 system.And install it on guest with windows10,but i can't work well.
Steps to reproduce:
1. ./configure --cross-prefix=x86_64-w64-mingw32- --enable-guest-agent-msi --with-vss-sdk=/root/vssdk/VSSSDK72 
   
  my vssdk download from:[vssdk](https://www.microsoft.com/en-us/download/details.aspx?id=23490),i install it on my pc and copy to /root/vssdk/VSSSDK72 
   
2. make qemu-ga -j4

3. and then install qemu-ga-x86_64.msi on windows10,it report the error:
   ![image](/uploads/b03b95e7b1b4519a153deadfbbaec751/image.png)

4.then I ./configure not with "--with-vss-sdk",the qemu-ga-x86_64.msi can install successfully.

5.So, I install gga first. Then ./configure with "--with-vss-sdk" to make get the qemu-ga.exe

6.replace qemu-ga.exe and reboot gga service,then execute the command "virsh domfsfreeze" on host,but it report error:

   error: Unable to freeze filesystems
   error: internal error: unable to execute QEMU agent command 'guest-fsfreeze-freeze': failed to add \\?\Volume{d1ee1072-0000-0000-0000-100000000000}\ to snapshot set: 


**I looked at the windows Event Viewer,it get the error:**

   Unexpected error querying for the IVssWriterCallback interface. hr = 0x80070005, Access is denied.

I have referred to this [document](https://www.ryadel.com/en/volume-shadow-copy-service-error-unexpected-error-querying-for-the-ivsswritercallback-interface-how-to-fix-that/),but it not work.