bootstrap.conf: drop gnulib tests from libvirt

bootstrap.conf: drop gnulib tests from libvirt

We are in process of removing gnulib and adopting meson as our build
system.  In order to help with the transition let's drop gnulib tests.

This will also help with the fact that before we will be able to drop
gnulib completely we will store output of bootstrap in git.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>