Query for device and then set the blockdev name.

Query for device and then set the blockdev name.

IOshark uses /proc/diskstats to get various stats. It needs a
block device name for doing this. The block device was hardcoded
as sda (Marlin/Sailfish). Query the device productname and use
this to set the block device name instead. Needed to make IOshark
work on non-M/S device.

Test: Testing the change on marlin as well as bullhead (which
covers Sailfish, Shamu and Angler as well).

Change-Id: Id9d7071019112cede1fd5e5c1f2c62f2fc4b6e65
Signed-off-by: Mohan Srinivasan <srmohan@google.com>