DataUsageSummary: fix mobile data usage display for sim-less devices

- Don't assume the device has a sim card. Check for a phone number
  instead. Otherwise the mobile data usage screen will not show up
  on sim-less CDMA devices.

Change-Id: Ic6e35dc209ff05e0c89dc990ad82f4ab4d3f337d
Use a hashed MAC address instead of IMEI for stats collection.

PS2: always use hashed Wifi MAC address to avoid zombies when wiping

Change-Id: I7379c5b380273e35b5aab582f5268d6946e0a255