tools: Don't list virsh-* under EXTRA_DIST

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>