LU-16460 lnet: validate data sent from user land properly

LU-16460 lnet: validate data sent from user land properly

Testing with improper setting from user land exposed some bugs in
the kernel's code handling of these cases. For tunables sent from
user land we need to do proper range checking. An improper cast
in the new Netlink tunables code preventing setting the default
LND tunable settings. Also silently ignore trying to set LND
tunables when its not supported. We shouldn't stop NI setup in
this case. Lastly setup the NI tunables to -1 when user land
doesn't provide any input. This tells the LND driver to use it
default values for the tunables. Resolve a double free when
setting up a NI with a non-existing interface. Another fix is for
net locking in lnet_net_cmd().

For lnetctl fix the YAML handling when only conns_per_peer is
requested. I only tested conns_per_peer and NI tunables changes
together before which missed the mentioned case.

Fixes: 8f8f6e2f3 ("LU-10003 lnet: use Netlink to support old and new NI APIs.")
Test-Parameters: trivial testlist=sanity-lnet
Change-Id: I7c5e993de57e3d674ecb8e3cc1bd62506470d416
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/49588
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>