LU-8035 obd: rename md_getstatus() to md_get_root()

LU-8035 obd: rename md_getstatus() to md_get_root()

Finish the partial renaming of the the OBD MD method md_getstatus() to
md_get_root().

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Iadd785ce774377d3dba40f64dbddaaf68cfc8087
Reviewed-on: http://review.whamcloud.com/19824
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Wang Shilong <wshilong@ddn.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>