tools: Don't list virsh-* under EXTRA_DIST
    
    When we wanted to break huge and unmaintainable virsh into
    smaller files first thing we did was to just move funcs into
    virsh-.c files and then #include them from virsh. Having it done
    this way we also needed to have them listed under EXTRA_DIST.
    However, things got changed since then and now all the virsh-*.c
    files are proper source files. Therefore they are listed under
    virsh_SOURCES too. But for some reason we forgot to remove them
    from EXTRA_DIST.
    
    Signed-off-by: Michal Privoznik <mprivozn@redhat.com>