LU-957 scrub: Proc interfaces and tests for OI scrub

LU-957 scrub: Proc interfaces and tests for OI scrub

1) Control/trace OI scrub running.

2) Verify whether the OI scrub basic functions works or not.

3) Test OI scrub performance.

For autotest:
Test-Parameters: testlist=sanity-scrub,scrub-performance

Signed-off-by: Fan Yong <yong.fan@whamcloud.com>
Change-Id: I5be3d1a521f5f7875f56e9455ff2010016e6a344
Reviewed-on: http://review.whamcloud.com/3168
Reviewed-by: Yu Jian <yujian@whamcloud.com>
Tested-by: Hudson
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>