LU-16160 llite: SIGBUS is possible on a race with page reclaim

LU-16160 llite: SIGBUS is possible on a race with page reclaim

We can restart fault handling if page truncation happens
in parallel with the fault handler.

Lustre-change: https://review.whamcloud.com/49647
Lustre-commit: b4da788a819f82d35b685d6ee7f02809c05ca005

Include updates to rw_seq_cst_vs_drop_caches.c from 5b911e0326
to add the '-m' option to test mmap IO operations in sanityn/16g.

Change-Id: I6e60783e3334f87e799dc8b0e6e63d0bb358a236
Signed-off-by: Andrew Perepechko <andrew.perepechko@hpe.com>
Signed-off-by: Patrick Farrell <farr0186@gmail.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/49831
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>