tools: Build and install disktool only on the server
tools: Build and install disktool only on the server

- disktool is only used on the server, so don't build/install it on the
client

cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr,cmusatyalab/openisr