LU-16046 ldlm: group lock unlock fix

LU-16046 ldlm: group lock unlock fix

The original LU-9964 fix had a problem because with many pages in
memory grouplock unlock takes 10+ seconds just to discard them.

The current patch makes grouplock unlock thread to be not atomic, but
makes a new grouplock enqueue to wait until previous CBPENDING lock
gets destroyed.

HPE-bug-id: LUS-10644
Signed-off-by: Vitaly Fertman <vitaly.fertman@hpe.com>
Change-Id: I7798138b953320c477ce60c4e34eac40ada95a69
Reviewed-on: https://es-gerrit.dev.cray.com/161411
Reviewed-by: Andriy Skulysh <c17819@cray.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Tested-by: Alexander Lezhoev <alexander.lezhoev@hpe.com>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/49008
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexander <alexander.boyko@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>