Add logic to handle screenshot file creation failure

Delete the bugreport file to free the space before returning.

Delete unnecessary if blocks as the File constructor would never return
null

Bug:123617758
Test: Force code to execute the if (screenshotFd == null) block.
      Bugreport file gets deleted successfully

Change-Id: Ib88278a8a56799ef562b8b06e5e530a8e31e85d5