wni: use win32net module for creating new user
wni: use win32net module for creating new user

This require UAC disabled (or already started as administrator), but
works much more reliable ("net user" sometimes fails _silently_).

QubesOS/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin