block: Fix bdrv_find_backing_image()

bdrv_find_backing_image() should use bdrv_get_full_backing_filename() or
bdrv_make_absolute_filename() instead of trying to do what those
functions do by itself.

path_combine_deprecated() can now be dropped, so let's do that.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 20190201192935.18394-14-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
1 file changed