tools/kvm_stat: hide cursor

When running kvm_stat in interactive mode, the cursor appears at the lower
left corner, which looks a bit distracting.
This patch hides the cursor by turning it invisible.

Signed-off-by: Stefan Raspl <raspl@linux.vnet.ibm.com>
Reviewed-By: Sascha Silbe <silbe@linux.vnet.ibm.com>
Reviewed-by: Marc Hartmayer <mhartmay@linux.vnet.ibm.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>