Re: [Libguestfs] [PATCH] builder, sysprep: initialise the random generator

virt-builder and virt-sysprep may make use of Common_utils.string_random8 (which uses Random.int) for constructing temporary paths; not initialising the random generator means that every invocation will reuse the same name used previously (!). Thus just call Random.self_init, just like virt-sparsify already does. Expand the test-virt-sysprep-script.sh test to ensure that virt-sysprep is not affected again by this issue.