sr: Fix screen flashing during wipe operations

 * Clear buffer in draw_progress_locked() and always call this in
   update_progress_locked().  This is necessary to ensure that all
   backing frames in the graphics implementation get updated because
   we aren't guaranteed to have any particular number of backing
   frames.

 * Remove dialogs on wipe operations since we are using the progress
   animation now.

 * Set progress indicator after showing "Formatting" text to avoid
   momentary flicker.

Change-Id: I0efb22ea5a64eb53a0323361bc5fc9c0aac56420