qemu: Defer support checks for external active snapshots to blockdev code or qemu
qemu: Defer support checks for external active snapshots to blockdev code or qemu

Remove libvirt's support check for the target of an external snapshot to
the blockdev code or qemu. This will potentially require a more complex
cleanup but removes a level of hardcoded feature checks.

Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>

olafhering/libvirt,nertpinx/libvirt,zippy2/libvirt,crobinso/libvirt,jardasgit/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,libvirt/libvirt,zippy2/libvirt,olafhering/libvirt,andreabolognani/libvirt,jfehlig/libvirt,libvirt/libvirt,olafhering/libvirt,andreabolognani/libvirt,jfehlig/libvirt,jfehlig/libvirt,zippy2/libvirt,jardasgit/libvirt,nertpinx/libvirt,zippy2/libvirt,jfehlig/libvirt,olafhering/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,crobinso/libvirt,fabianfreyer/libvirt,andreabolognani/libvirt,libvirt/libvirt,jardasgit/libvirt,libvirt/libvirt,crobinso/libvirt,andreabolognani/libvirt,jardasgit/libvirt,crobinso/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt