Fix bug #1254 - write list not working under share-level security

Fix bug #1254 - write list not working under share-level security
A somewhat more elegant fix than I could use for 3.2.x or 3.0.x.
Turns out the only part of check_user_ok() that needs to change
for share level security is the VUID cache pieces, so I can just
always use check_user_ok() for all lp_security() cases.
Jeremy
(cherry picked from commit a808c53ec938a6aeb9f9ddc6a5a02273c7bfdcc9)