s3:lib/gencache: place gencache.tdb into /var/cache/samba

s3:lib/gencache: place gencache.tdb into /var/cache/samba

/var/lock/samba is located on tmpfs on newer systems,
but we want to keep things like the server affinity cache
across reboots.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
(cherry picked from commit 54529fd354275cfb4ece407f95ef34675b202ea3)

Fix bug #9802 - gencache.tdb should be moved to /var/cache/samba.

Autobuild-User(v4-0-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-0-test): Mon Sep  2 11:57:51 CEST 2013 on sn-devel-104