backup: pass in valid dummy pid for LWP

backup: pass in valid dummy pid for LWP

LWP_CreateProcess needs memory passed in; instead of a null pointer,
pass in a pointer to a PROCESS.

Reviewed-on: http://gerrit.openafs.org/3555
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 4f89d4ad348f1b20b9f27e8985fa09eafb6212e0)
Change-Id: I10c81fc3242294266468560628ff4f328e6e6997
Reviewed-on: http://gerrit.openafs.org/3560