LU-17000 obdclass: Add NULL check for parms under class_exp2cliimp

LU-17000 obdclass: Add NULL check for parms under class_exp2cliimp

This patch adds NULL pointer check for parameters
passed under class_exp2cliimp()

Test-Parameters: trivial
CoverityID: 424699 ("Dereference before null check")
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: Ie7d96c10086959a3f31b290d56621261da480a36
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/55030
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>