LU-12678 o2iblnd: fix bug in list_first_entry() change.

LU-12678 o2iblnd: fix bug in list_first_entry() change.

This comparison should be != NULL, else a NULL pointer could be
dereferenced.

Test-Parameters: trivial
Fixes: 34b57a6f8fcd ("LU-12678 lnet: use list_first_entry() in lnet/klnds subdirectory.")
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I4510e2e0f2eb7b5bf86626e5ddb5ee537d3fae02
Reviewed-on: https://review.whamcloud.com/43558
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Tested-by: Maloo <maloo@whamcloud.com>