LU-2037 tests: Wait for devices to initialize on test setup

Fix an issue where we do not wait for a device to
initialize before getting the label. This label then does
not correspond to an actual device.
A check is now done on the label names to see
if you are getting back the 'ffff' which signifies that the
device has not finished initializing yet. In this case
we will wait and retry in 1,3,5,10 seconds or until
the command succeeds.

Xyratex-bug-id: MRP-546
Reviewed-by: Iurii Golovach <Iurii_Golovach@xyratex.com>
Reviewed-by: Kyrylo Shatskyy <Kyrylo_Shatskyy@xyratex.com>
Signed-off-by: Michael McKay <michael_mckay@xyratex.com>
Change-Id: I01e045227a4b3b6e007dcc9685238a5425cdffe8
Reviewed-on: http://review.whamcloud.com/4111
Reviewed-by: Yu Jian <yujian@whamcloud.com>
Tested-by: Hudson
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>