plugins/clnrest: disable ourselves unless rest-port is set.

This mirrors grpc's behavior, and avoids listening on ports without
explicit user permission.

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

plugins/clnrest/clnrest.py

@@ -110,7 +110,10 @@ def start_server():
 
 @plugin.init()
 def init(options, configuration, plugin):
-    set_config(options)
+    # We require options before we open a port.
+    err = set_config(options)
+    if err:
+        return {'disable': err}
     start_server()