LU-17760 lnet: Crash caused by uninitialized interface name

LU-17760 lnet: Crash caused by uninitialized interface name

When adding an interface with ip2net, a duplicate configuration of an
already existing interface can cause a crash or misconfiguration of
lnet. Incoming interface names have to be checked if they are null and
furthermore duplicate interface configurations have to be removed.
When a duplicate is detected add has to be added to a list to be able
to shut it down otherwise shutdown would assert.
The problem can be repoduced on tcp and o2ib networks.
Steps that were used to reproduce the problem in the original
configuration, but it is reproducable in other variations and
in tcp networks.
modprobe lnet
lnetctl lnet configure
lnetctl net add --net  o2ib --if mlxib1
lnetctl net add --net  o2ib --if mlxib1
       --ip2net "o2ib 172.30.12.*"

Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Frank Sehr <fsehr@whamcloud.com>
Change-Id: Ie76d97cc52855ab897a9e07a3697483189d4b19e
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54859
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Cyril Bordage <cbordage@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>