Without knowing what method was called, we can't have useful general logging
methods, so go through the pain of adding "const char *method" everywhere,
and add:
1. ignore_and_complete - we're done when jsonrpc returned
2. log_broken_and_complete - we're done, but emit BROKEN log.
3. plugin_broken_cb - if this happens, fail the plugin.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>