adb: host: Provide better sideload status

 * Show data transfer in MB and in multiple of the file size.

 * Show a spinner to indicate liveness, which is updated at least once
   per second regardless of data transfer.

 * Do not allow sideload of zero sized files.

Change-Id: I1bd0df6a8183fad5a502fc26a7e789c27d24f71a