LU-930 iokit: remove obsolete obdsurvey reference

LU-930 iokit: remove obsolete obdsurvey reference

Remove reference to long obsolete "obdsurvey" tool from README.

Fixes: c8521aa1599c ("Removed per Peter Bojanic...")
Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ic95e0544b725ff9a83e8865d9913af51336b4655
Reviewed-on: https://review.whamcloud.com/47102
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: cliff white <cwhite@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>