qemu_vhost_user: don't raise error for unknown features
qemu_vhost_user: don't raise error for unknown features

Similar to what was done for qemu_firmware.c in 61d95a1073, don't
report an error for unknown vhost-user features, just log it and
correctly continue on

Reviewed-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Signed-off-by: Cole Robinson <7cd45ff6ad1fb7cf556a02797d774247851499f8@redhat.com>

libvirt/libvirt,olafhering/libvirt,crobinso/libvirt,crobinso/libvirt,nertpinx/libvirt,olafhering/libvirt,nertpinx/libvirt,jfehlig/libvirt,crobinso/libvirt,zippy2/libvirt,zippy2/libvirt,olafhering/libvirt,nertpinx/libvirt,libvirt/libvirt,jfehlig/libvirt,libvirt/libvirt,zippy2/libvirt,nertpinx/libvirt,nertpinx/libvirt,crobinso/libvirt,zippy2/libvirt,jfehlig/libvirt,jfehlig/libvirt,libvirt/libvirt,olafhering/libvirt