LU-12511 lnet: rework lnd module loading

LU-12511 lnet: rework lnd module loading

The kernel IS_MODULE() only works in the positive, ie no ifndef.
So rework the LND module loading code to handle if modules are
enabled.

Test-Parameters: trivial testlist=sanity-lnet
Change-Id: Ie97b00b6b5c21d6e20acf72f796707630369251e
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/57946
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: Serguei Smirnov <ssmirnov@whamcloud.com>
Reviewed-by: Chris Horn <chris.horn@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>