LU-17887 obd: do not update obd_memory from RCU

LU-17887 obd: do not update obd_memory from RCU

OBD_FREE_PRE() should not be run from an RCU
callback as the obdclass module may have been
unloaded during the RCU grace period.

Signed-off-by: Bruno Faccini <bfaccini@nvidia.com>
Change-Id: I6f663b2aed2e60c15f2a1b9755b2c4050bd91ce2
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/55263
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>