LU-16557 client: -o network needs add_conn processing

LU-16557 client: -o network needs add_conn processing

Mount option -o network restricts client import to use
only selected network. It processes connection UUID/NIDs
during 'setup' config command handling but skips any
'add_conn' command if its UUID has no mention about that
network. Meahwhile connection UUID is just a name and may
have many NIDs configured including those on restricted
network which are skipped as well. Therefore client import
configuration misses failover NIDs on restricted network.

Patch makes import to save restricted network information
after 'setup' command processing, so it is applied to any
client_import_add_conn() call. The 'add_conn' command is
always processed now and its NIDs will be filtered in the
same way as for 'setup'.
Test 31 in sanity-sec.sh is extended to check imports
failover_nids has all and only NIDs on restricted network

Lustre-change: https://review.whamcloud.com/49986
Lustre-commit: c508c9426838f16256223ab0bbd648bfbec25e46

Test-Parameters: env=ONLY=31 testlist=sanity-sec
Signed-off-by: Mikhail Pershin <mpershin@whamcloud.com>
Change-Id: Id70ebd836f061f154e3779b07b52f1baea9a1776
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Cyril Bordage <cbordage@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/50172
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>