LU-13895 lnet: Prevent discovery on peer marked deletion

LU-13895 lnet: Prevent discovery on peer marked deletion

If a peer has been marked for deletion then we needn't perform any
other discovery operation on it. Integrate this peer state into the
top level of the discovery state machine so that it is checked before
any other state.

Lustre-change: https://review.whamcloud.com/39604
Lustre-commit: aa7de0af6969df77a896e3a2e90c971a5081e324

HPE-bug-id: LUS-9192
Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: Ie9de5b0d38d720f4f49d7e4a0673a6b52f9d3d80
Reviewed-on: https://review.whamcloud.com/48291
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>