wmaster isn't actually a usable network device; it's the master device for
things like sniffers and such.  Only actual 802.11 STA devices (ie, wlanX or
ethX) should be shown because those are the ones that can actually be configured.

You can distinguish between the two by checking the 'type' field of each
device's sysfs directory (ie /sys/class/net/wlan0/type).  A type '1' is usable,
but whatever type wmasterX uses is not.  I'd recommend just excluding whatever
type wmasterX is rather than only letting type 1 through.