LU-17895 lnet: Validate input for lnetctl import

LU-17895 lnet: Validate input for lnetctl import

Add validation of the input being parsed by lnetctl import when it is
expecting the global parameters. This resolves segmentation faults
when it encounters bad or missing keys and values.

Test-Parameters: trivial testlist=sanity-lnet
Signed-off-by: Chris Horn <chris.horn@hpe.com>
Change-Id: I232daed773283ea89e9815bf6bd79526dfd5fd4f
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/55340
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Frank Sehr <fsehr@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>