Show ProgressDialog when waiting for radio to turn on when provisioning.

Turning on the cellular radio when user selects the provisioning notification
can take 30-60s so a UI is needed to keep the user informed that the radio is
coming up.  This is only for provisioning APN support (only AT&T tablets now).

bug:15990642
Change-Id: I1e77c3a1b1a24be7acc7cb3c925c002e5fa2d1a9