LU-11518 osc: Do ELC on locks with no OSC object

LU-11518 osc: Do ELC on locks with no OSC object

Currently, osc_ldlm_weigh_ast weighs locks with no OSC
object in their ast data as "1", meaning the lock is not
considered for ELC.

This doesn't make much sense, since if there is no OSC
object, it's unlikely there's any data under the lock, so
it's actually a good candidate for ELC.

Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: Ie832afbf2479f3a348e44d2c21992696830000ae
Reviewed-on: https://review.whamcloud.com/34584
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Gu Zheng <gzheng@ddn.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>