Fix network configuration

Previously, attempting to configure a second interface (with a static ip address) would result in the following output with VAGRANT_LOG=debug:

    DEBUG configure_networks: vm_interface_map: {1=>{:name=>"Local Area Connection", :mac_address=>"080027AB52FB", :interface_index=>"12", :index=>"7"}, 2=>{:name=>"Local Area Connection 2", :mac_address=>"08
    002753A4C3", :interface_index=>"13", :index=>"8"}}
     INFO winrmshell: Configuring NIC  using static ip 10.20.1.60
    DEBUG winrmshell: powershell executing:
    netsh interface ip set address "" static 10.20.1.60 255.255.255.0
    DEBUG winrmshell: Exit status: 1

The issue appears to have been caused by variable name mis-match introduced in some recent changes. With the modifications in this commit, the same debug output now shows (as expected):

    DEBUG configure_networks: vm_interface_map: {1=>{:name=>"Local Area Connection", :mac_address=>"080027AB52FB", :interface_index=>"12", :index=>"7"}, 2=>{:name=>"Local Area Connection 2", :mac_address=>"08
    002753A4C3", :interface_index=>"13", :index=>"8"}}
     INFO winrmshell: Configuring NIC Local Area Connection 2 using static ip 10.20.1.60
    DEBUG winrmshell: powershell executing:
    netsh interface ip set address "Local Area Connection 2" static 10.20.1.60 255.255.255.0
    DEBUG winrmshell: Exit status: 0