tools: Make symlinks to vsh bash-completion script

tools: Make symlinks to vsh bash-completion script

The bash-completion project documents that only those scripts
from $BASH_COMPLETIONS_DIR that share name with the current
command for which <TAB> was hit are loaded [1]. This means, that
vsh script we have there is not loaded. We have to create
symlinks for virsh and virt-admin.

At the same time, we have to create new RPM package because
virt-admin and client packages are independent. That means we
cannot place the vsh script in either of them. What we can do is
to have a different package that contains the completion script
and then virt-admin and client packages contain only the symlink
and require the bash-completion package.

1: https://github.com/scop/bash-completion#faq

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>