Toggles: fix logic to check if usb tether is active

Change-Id: I703f2f14e3587620c44df5bf0f7030a9fe3c0041
Signed-off-by: Dirk Rettschlag <dirk.rettschlag@gmail.com>
Merge branch 'kitkat' of github.com:AOKP/frameworks_base into kitkat