ctdb-scripts: Avoid shellcheck warning SC2154 (unassigned variables)

ctdb-scripts: Avoid shellcheck warning SC2154 (unassigned variables)

SC2154: VAR is referenced but not assigned.

Change ctdb_setup_service_state_dir(), ctdb_get_pnn() and
ctdb_get_ip_address() to print the value so it can be assigned to a
variable.  The performance gain from avoiding the sub-shells when
calling these functions is close to zero.

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