LU-15538 lnet: DLC sets map_on_demand incorrectly

LU-15538 lnet: DLC sets map_on_demand incorrectly

When any NET or LND tunable is specified via CLI or yaml, then the
whole tunables struct gets memset to 0, or in the case of yaml config,
0 gets assigned to any tunable that isn't specified in the yaml. This
causes a problem for map_on_demand because 0 is a valid value for that
parameter, and ko2iblnd cannot know whether the user specified that 0
should be used or if DLC is specifying that the parameter was unset.

Rather than setting this parameter to 0 in the LND tunables struct,
have DLC set it to UINT_MAX to indicate that ko2iblnd should use the
value of the kernel module parameter.

Lustre-change: https://review.whamcloud.com/46492
Lustre-commit: 896f4a082b93453f5e7168f685faff4fba594ff3

Test-Parameters: trivial
HPE-bug-id: LUS-10740
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: I303e64d4d402ba61b5ae3e3910873f192a4a2845
Reviewed-on: https://review.whamcloud.com/48491
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: Cyril Bordage <cbordage@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>