fix(osfamilymap): use `whoami` for Windows `rootuser`

Fix #495

salt/osfamilymap.yaml

 {%-   set rootuser = salt['cmd.run']("stat -f '%Su' /dev/console") %}
 {%-   set rootgroup = salt['cmd.run']("stat -f '%Sg' /dev/console") %}
 {%- elif grains.os_family == 'Windows' %}
-{%-   set rootuser = salt['cmd.run']("id -un") %}
+{%-   set rootuser = salt['cmd.run']("whoami").split("\\")[1] %}
 {%- endif %}