LU-6142 ldlm: remove unused ldlm_server_conn

LU-6142 ldlm: remove unused ldlm_server_conn

This field is never set or used, so remove it.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.com>
Change-Id: I1421914e487372eecb501e2483aeed07f56788e8
Reviewed-on: https://review.whamcloud.com/35883
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.super@gmail.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>