Revert "Handle locking for assoc_mgr_clear_used_info() upstream."

Leads to deadlock in 'scontrol reconfigure':

0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
1  0x00007f61b1880801 in __GI_abort () at abort.c:79
2  0x00007f61b1fe2bd7 in __xassert_failed (expr=expr@entry=0x7f61b1ff2989
"_store_locks(locks)", file=file@entry=0x7f61b1ff2e80
"../../../../slurm/src/common/assoc_mgr.c",
    line=line@entry=2114, func=func@entry=0x7f61b1ff4bf8 <__func__.17903>
"assoc_mgr_lock") at ../../../../slurm/src/common/xassert.c:57
3  0x00007f61b1ead017 in assoc_mgr_lock (locks=locks@entry=0x7f61ad6da610) at
../../../../slurm/src/common/assoc_mgr.c:2114
4  0x00005632675e4509 in _adjust_limit_usage (type=type@entry=0,
job_ptr=job_ptr@entry=0x7f6190015000) at
../../../../slurm/src/slurmctld/acct_policy.c:719
5  0x00005632675e4b49 in acct_policy_add_job_submit
(job_ptr=job_ptr@entry=0x7f6190015000) at
../../../../slurm/src/slurmctld/acct_policy.c:2515
6  0x00005632676767c7 in _restore_job_dependencies () at
../../../../slurm/src/slurmctld/read_config.c:2612
7  read_slurm_conf (recover=recover@entry=1, reconfig=reconfig@entry=true) at
../../../../slurm/src/slurmctld/read_config.c:1310
8  0x0000563267668d0f in _slurm_rpc_reconfigure_controller
(msg=msg@entry=0x7f61ad6dade0) at
../../../../slurm/src/slurmctld/proc_req.c:3645
9  0x000056326766f646 in slurmctld_req (msg=0x7f61ad6dade0,
arg=0x7f619c000dc0) at ../../../../slurm/src/slurmctld/proc_req.c:425
10 0x00005632675efbc9 in _service_connection (arg=<optimized out>) at
../../../../slurm/src/slurmctld/controller.c:1285
11 0x00007f61b1c386db in start_thread (arg=0x7f61ad6db700) at
pthread_create.c:463
12 0x00007f61b196188f in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:95

Bug 5469.

This reverts commit 4b7ad3b6.