LU-17230 socklnd: treat UNKNOWN netif operstate as UP

LU-17230 socklnd: treat UNKNOWN netif operstate as UP

"UNKNOWN" (IF_OPER_UNKNOWN) operational state doesn't necessarily
mean that the interface can't be used and may be the result of
particular network driver not providing UP/DOWN states,
so it may be incorrect for socklnd to initiate
setting of a "fatal error" flag on a NI using an interface
in "UNKNOWN" operstate.

Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Change-Id: I39dfa01f3758809440d50cf8b6b11555889ef366
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52842
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Cyril Bordage <cbordage@whamcloud.com>