Make goodhosts really work with Hyper-V

[YouJiacheng]

Really solve #40 , use read_guest_ip to handle Hyper-V with dynamic IP. Original @machine.config.vm.provider :hyperv do ... end's block is never executed since provider configuration blocks are only possible to be executed in a very early stage(far before VM boot, while goodhosts is triggered after VM up, and read_guest_ip need a booted VM), and its read_guest_ip usage is incorrect(Hyper-V driver's read_guest_ip accept 0 argument).

Also:

• Remove useless networks.empty? check, since there is always the default forwarded_port network for ssh.
  • Note this removal does NOT make the code vulnerable, since networks.each do |network| .... end do nothing if networks is empty.
• Correct action hooks timing: "add" after "up" should correspond to "remove" before "halt".
  • Without this, we cannot RemoveHosts when halting or destroying Hyper-V VM, since read_guest_ip can only work with running or suspended VMs.

[Mte90]

I am ok for this PR but I cannot do any test for hyper-v as I don't have any windows machine.

What do you think @tomjn to me the code is fine as we are just prepending everything.

[Mte90]

New release avalaible :-)