qemu: snapshot: Forbid internal snapshot with passthrough devices
qemu: snapshot: Forbid internal snapshot with passthrough devices

When attempting to create internal system checkpoint with a passthrough
device qemu will report the following error:

error: operation failed: Error -22 while writing VM

This patch calls the function to check if migration is possible with
given VM and thus improves the error to:

error: Requested operation is not valid: domain has assigned non-USB host devices

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=874418#c19
Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>

eskultety/libvirt,libvirt/libvirt,datto/libvirt,jfehlig/libvirt,elmarco/libvirt,andreabolognani/libvirt,eskultety/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,rlaager/libvirt,rlaager/libvirt,eskultety/libvirt,taget/libvirt,datto/libvirt,taget/libvirt,elmarco/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt,rlaager/libvirt,shugaoye/libvirt,andreabolognani/libvirt,nertpinx/libvirt,rlaager/libvirt,olafhering/libvirt,elmarco/libvirt,agx/libvirt,datto/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,shugaoye/libvirt,taget/libvirt,nertpinx/libvirt,zippy2/libvirt,shugaoye/libvirt,zippy2/libvirt,nertpinx/libvirt,nertpinx/libvirt,elmarco/libvirt,libvirt/libvirt,taget/libvirt,zippy2/libvirt,jardasgit/libvirt,jardasgit/libvirt,crobinso/libvirt,olafhering/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,agx/libvirt,jardasgit/libvirt,agx/libvirt,fabianfreyer/libvirt,datto/libvirt,agx/libvirt,crobinso/libvirt,libvirt/libvirt,taget/libvirt,shugaoye/libvirt,crobinso/libvirt,libvirt/libvirt,crobinso/libvirt,jfehlig/libvirt,eskultety/libvirt,jardasgit/libvirt,olafhering/libvirt,andreabolognani/libvirt,zippy2/libvirt,rlaager/libvirt,agx/libvirt,datto/libvirt,VenkatDatta/libvirt,eskultety/libvirt,olafhering/libvirt,shugaoye/libvirt,elmarco/libvirt,jfehlig/libvirt,VenkatDatta/libvirt