According to the specification[1], the setting name is 'addresses', not
'address'. The later apparently worked on some NetworkManager versions,
but for example not on the one in Debian wheezy. Also fix value
format (IP;netmask;gateway).
[1] htts://developer.gnome.org/NetworkManager/unstable/ref-settings.html
FixesQubesOS/qubes-issues#1280