LU-8191 lnet: remove unused, fix non-static functions

LU-8191 lnet: remove unused, fix non-static functions

lnet_selftest_structure_assertion() and
lnet_net_is_pref_rtr_locked() are never called.
This patch removes both functions.

Static analysis shows that a number of functions
could be made static. This patch also declares
several functions in lnet static.

Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: Ie1b49c5652553715cd9f96b56090d33a95e3b438
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51436
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: jsimmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>