wpa_supplicant: run as 'wifi' user.

Android runs wpa_supplicant as the 'wifi' user. Let's do the same.
Weave provisioning seems to still work. Not sure why we didn't do this
in the first place.

Bug: 26337609
Change-Id: Ia761063fbbe34c31de61b7860425c0921fd46eec
2 files changed