LU-18508 obdclass: llog test to set lpi_rc

LU-18508 obdclass: llog test to set lpi_rc

llog_test_process_thread() should set lpi_rc before signalling own
completion, otherwise the caller can find uninitialized lpi_rc.

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: Id49f10bb0454da2bdf047a2c83e4c0462b826018
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/57274
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Mikhail Pershin <mpershin@whamcloud.com>