traffic_replay: Generate users faster by writing to local DB

traffic_replay: Generate users faster by writing to local DB

We can create user accounts much faster if the LDB connection talks
directly to the local sam.ldb file rather than going via LDAP. This
patch allows the 'host' argument to the tool to be a .ldb file (e.g.
"/usr/local/samba/private/sam.ldb") instead of a server name/IP.

In most cases, the traffic_replay tool wants to run on a remote device
(because the point of it is to send traffic to the DC). However, the
--generate-users-only is one case where the tool can be run locally,
directly on the test DC. (The traffic_replay user generation is handy
for standalone testing, because it also handles assigning group
memberships to the generated user accounts).

Note that you also need to use '--option="ldb:nosync = true"' to get
the improvement in performance.

Signed-off-by: Tim Beale <timbeale@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>