LU-14188 osd: remove not used iam_container lock

LU-14188 osd: remove not used iam_container lock

There is an rw_semaphore
struct iam_container {
    ...
        /*
         * read-write lock protecting index consistency.
         */
        struct rw_semaphore     ic_sem;   <<<<<<
        struct dynlock       ic_tree_lock;
        /* Protect ic_idle_bh */
        struct mutex         ic_idle_mutex;
     ...
};

There is initialization
 2    234  lustre/osd-ldiskfs/osd_iam.c <<iam_container_init>>
             init_rwsem(&c->ic_sem);

There are wrappers
   3    622  lustre/osd-ldiskfs/osd_iam.c <<iam_container_write_lock>>
             down_write(&ic->ic_sem);
   4    627  lustre/osd-ldiskfs/osd_iam.c <<iam_container_write_unlock>>
             up_write(&ic->ic_sem);
   5    632  lustre/osd-ldiskfs/osd_iam.c <<iam_container_read_lock>>
             down_read(&ic->ic_sem);
   6    637  lustre/osd-ldiskfs/osd_iam.c <<iam_container_read_unlock>>
             up_read(&ic->ic_sem);

But this wrappers are not used. And, based on the git history, never been used.
Let's delete this useless code.

Change-Id: Ied1122f034e53fee08888e1091f700bda4507f00
Signed-off-by: Artem Blagodarenko <artem.blagodarenko@hpe.com>
HPE-bug-id: LUS-9545
Reviewed-on: https://review.whamcloud.com/40890
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>