LU-14810 lnet: ongoing push when discovery is stopped

LU-14810 lnet: ongoing push when discovery is stopped

If a push is not completed when discovery thread is stopped, then we
still have ln_dc_handler used as md handler (from
lnet_peer_send_push). That leads to assert failure from
lnet_assert_handler_unused.

To fix that, we call lnet_assert_handler_unused only after the monitor
thread has been stopped. Thus, the patch for LU-17496 is not needed
anymore.

Lustre-change: https://review.whamcloud.com/54884
Lustre-commit: 3ba393a5cb21ff0f8bd8a09c341ee01e936321c7

Fixes: 36b14a23a6 ("LU-17207 lnet: race b/w monitor thr stop and discovery push")
Test-Parameters: testlist=sanity-lnet env=ONLY="212 220",ONLY_REPEAT=100
Signed-off-by: Cyril Bordage <cbordage@whamcloud.com>
Change-Id: I426c37b12a3d29327a7295f528a5b875a9ac88a0
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/55167
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>