LU-12614 ldlm: ldlm_cancel_hpreq_check should check lock count

LU-12614 ldlm: ldlm_cancel_hpreq_check should check lock count

Make sure the number of locks we are going to cancel fits into
the supplied buffer first.
This is similar to LU-12603, just in a different place.

Change-Id: Ifa2aa976ce8613217c739ef609de54538c57b5e9
Signed-off-by: Oleg Drokin <green@whamcloud.com>
Reported-by: Alibaba Cloud <yunye.ry@alibaba-inc.com>
Reviewed-on: https://review.whamcloud.com/35807
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Yunye Ry <yunye.ry@alibaba-inc.com>