LU-16046 revert: "LU-9964 llite: prevent mulitple group locks"

LU-16046 revert: "LU-9964 llite: prevent mulitple group locks"

This reverts commit aba68250a67a10104c534bd726f67b31a7f35692
since it makes group unlock synchronous what leads to poor performance
on shared file IO under group lock.

Signed-off-by: Vitaly Fertman <vitaly.fertman@hpe.com>
Change-Id: I4548986297c22e402acd051dbdf97fe58198d100
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/48037
Reviewed-by: Alexander <alexander.boyko@hpe.com>
Reviewed-by: Zhenyu Xu <bobijam@hotmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>