LU-691 tests: Fix OST index errors in test suite

LU-691 tests: Fix OST index errors in test suite

Several tests run do_facet ost which assumes ost is ost0 which does
not exist according to the way the test suite works. This patch
address several areas where the wrong ost index is used. This patch
also introduces some short hand functions to get OST properties
from the index. Those functions ensure ost1, ost10 and ost100 are
seen as different which is not always the case.

This patch is backported from commit 8afd35c of LU-691.

Test-Parameters: envdefinitions=SLOW=yes,ENABLE_QUOTA=yes testlist=lfsck,sanity,replay-single
Signed-off-by: James Simmons <uja.ornl@gmail.com>
Signed-off-by: Yu Jian <yujian@whamcloud.com>
Change-Id: I97d9554a99be25db0e4f550bf8071ddc981dddc4
Reviewed-on: http://review.whamcloud.com/4821
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Lai Siyao <laisiyao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>