netfilter: xt_qtaguid: update to fix network traffic indicators

copy paste from CyanogenMod/android_kernel_samsung_msm8660-common

:D
netfilter: xt_qtaguid: Allow tracking loopback

In the past it would always ignore interfaces with loopback addresses.
Now we just treat them like any other.
This also helps with writing tests that check for the presence
of the qtaguid module.

Signed-off-by: JP Abgrall <jpa@google.com>