LU-930 misc: update URLs in README

LU-930 misc: update URLs in README

Update the URLs in the README file to reference the pages at
https://wiki.lustre.org/ instead of the WC pages.

Test-Parameters: trivial
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I209956b74c19e8b1fd1c0f6d93b8b217073ebbe5
Reviewed-on: https://review.whamcloud.com/38985
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Peter Jones <pjones@whamcloud.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>