LU-12355 osd-ldiskfs: timespec_trunc removed

LU-12355 osd-ldiskfs: timespec_trunc removed

As part of the y2038 changes:

timespec64_trunc was added in kernel 4.17
inode i_Xtime values are timespec64 in kernel 4.18
timespec_trunc was removed in kernel 4.19

Harden the existing LC_INODE_TIMESPEC64 check and stop
using the deprecated timespec_trunc().

oti_time is set but never used, remove oti_time.

Linux-commit: 8efd6894ff089adeeac7cb9f32125b85d963d1bc
Linux-commit: 95582b00838837fc07e042979320caf917ce3fe6
Linux-commit: 976516404ff3fab2a8caa8bd6f5efc1437fed0b8

Test-Parameters: trivial
Change-Id: Idadbf6ddd9aedbd251d7bbbb5b1486d4aa757ac5
Signed-off-by: Shaun Tancheff <stancheff@cray.com>
Reviewed-on: https://review.whamcloud.com/35050
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>