When changing network mapping, delete no longer needed networks

[glennmatthews]

GLMATTHE-M-20W1:cot glmatthe$ bin/cot edit-hardware COT/tests/input.ovf -o network.ovf -N "new network"
Network new network is not currently defined. Create it? [y] y
Please enter a description for this network [new network] 
GLMATTHE-M-20W1:cot glmatthe$ bin/cot info network.ovf 
<snip>
Networks:
  VM Network
  new network

NICs and Associated Networks:
  GigabitEthernet1               : new network
  GigabitEthernet2               : new network
  GigabitEthernet3               : new network
<snip>

Network "VM Network" no longer has any NICs associated with it so COT may as well delete this network entry from the OVF.