LU-15162 osd: improve OI lookup concurrency

LU-15162 osd: improve OI lookup concurrency

replace inode->i_mutex with i_rwsem in osd_obj_map_lookup()

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: Id8df20e00ae254ea4dcf4b10415e1927fac6bd44
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/45353
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Artem Blagodarenko <ablagodarenko@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>