[RESTRICT AUTOMERGE] Update PROVISIONING_USE_MOBILE_DATA behaviour.

The new behaviour is the following:
1. For QR and NFC provisioning:
 1.1. If DPC download info is not supplied, go to the landing screen
 1.2. Else if wifi SSID is specified, go to landing screen
 1.3. Else if wifi connection already exists, go to landing screen
 1.4. Else if PROVISIONING_USE_MOBILE_DATA is set to true, go to
      landing screen, ManagedProvisioning will handle mobile
      internet connection during the provisioning process
 1.5. Else if wifi SSID is NOT specified in the provisioning extras,
      show the wifi picker, pick wifi connection and go to landing
      screen
2. Maintain existing behaviour for non-QR and non-NFC provisioning

Test: manually performed provisioning with and without a
data-enabled SIM card, with and without a wifi connection, and
with and without any connection
Test: manual QA verified
Fixes: 153442588

Change-Id: I94b3a7a68ae7bef3477eb98488b7e57140cb518d
(cherry picked from commit 6f3efc7f9b2bbedffb74a42009a0432a01334851)
5 files changed