buildserver: only auto-detect KVM in ./makebuildserver

Having a second, different KVM auto-detect routine in Vagrantfile will only
confuse things.  This also removes the direct call to the systemd utility.
1 job for fixes-on-the-way-to-kvm in 22 minutes and 11 seconds (queued for 1 minute and 44 seconds)
Status Job ID Name Coverage
  Test
passed #4514151
test

00:22:11