Revert the way to retrieve VM IP in Remote ESXi Builder

I changed the way to retrieve vm ip in #1046.
But it does not support the situation that VMware Tools isn't running on the VM.
So I'd like to revert it for now.
And I also document that the Remote ESXi Builder supports ESXi 5.1 and above.
The reasons are following:
* `esxcli network vm port list` command is available with ESXi 5.1 and above.
* AFIAK we can not get the ip with ESX 5.0 and below, if VMware Tools isn't running on the VM.