Prefer the binary qemu-system-* over qemu-kvm or kvm.

The kvm binary is deprecated, so we shouldn't use it if the newer binary exists.

INFO runner: Running action: #<Vagrant::Action::Builder:0x007fdf108a97f0>
/home/pittsb/.vagrant.d/gems/gems/vagrant-kvm-0.1.4/lib/vagrant-kvm/driver/driver.rb:333:in `create': Call to virDomainCreateWithFlags failed: internal error: process exited while connecting to monitor: W: kvm binary is deprecated, please use qemu-system-x86_64 instead (Libvirt::Error)