ctdb-scripts: Call out to ctdb_lvs helper from 91.lvs

ctdb-scripts: Call out to ctdb_lvs helper from 91.lvs

To keep this commit comprehensible, 91.lvs and the CTDB CLI tool are
temporarily inconsistent.  The tool will be made consistent in a
subsequent commit.

LVS now uses a configuration file specified by CTDB_LVS_NODES and
supports the same slave-only syntax as CTDB_NATGW_NODES.  LVS also
uses new variable CTDB_LVS_PUBLIC_IFACE instead of
CTDB_PUBLIC_INTERFACE.

Update unit tests and documentation.

Note that the --lvs and --single-public-ip daemon options are no
longer used.  These will be removed and relevant documentation
updated in a subsequent commit.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>