dlm: Add spaces for better code readability

The script "checkpatch.pl" pointed information out like the following.

CHECK: spaces preferred around that '+' (ctx:VxV)

Thus fix the affected source code places.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: David Teigland <teigland@redhat.com>