eventscript: use scripts array directly, rather than separate list

eventscript: use scripts array directly, rather than separate list

We rename ctdb_monitor_script_status to ctdb_script, and instead of
allocating them as the scripts are executed, we allocate them up front
and keep a "current" interator.

This slightly simplifies the code, though it means we only marshall up
to the last successfully run script.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>