Fix network configuration

[reidmv]

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

[sneal]

You're right, the capability does appear to be passing the wrong arg. Good timing, I was just about to write some unit tests for this class.

[reidmv]

Issue resolved in #97

(comment for posterity)