LU-15702 lov: remove lo_trunc_stripeno

LU-15702 lov: remove lo_trunc_stripeno

Remove the lo_trunc_stripeno member of struct lov_layout_raid0 and add
an lis_trunc_stripe_index array to struct lov_io. This makes the
truncate stripe index information belong to the IO and not to the
concurrently accessed object. This is needed because we do not have
locking that protects it from its initialization in lov_io_iter_init()
to its use in lov_lock_sub_init(). Also remove the unused
lo_write_lock member of struct lov_object.

Fixes: 9801500451 ("LU-14128 lov: correctly set OST obj size")
Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Change-Id: I799e07059212629fe9d84c5e58c349035a40da9e
Reviewed-on: https://review.whamcloud.com/46953
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>