Couple of fixes to the demo app. (#860)

First, make it so that when no failover is scheduled to happen during the
demo, we still show the summary at the end of it.

Second, install constraints and indexes to the demo app schema.

src/bin/pg_autoctl/demoapp.c

@@ -150,10 +150,15 @@ demoapp_prepare_schema(const char *pguri)
 	const char *ddls[] = {
 		"drop schema if exists demo cascade",
 		"create schema demo",
+
+		"create table demo.client(client integer primary key, pid integer, "
+		"retry_sleep_ms integer, retry_cap_ms integer, failover_count integer, "
+		"unique(pid))",
+
 		"create table demo.tracking(ts timestamptz default now(), "
-		"client integer, loop integer, retries integer, us bigint, recovery bool)",
-		"create table demo.client(client integer, pid integer, "
-		"retry_sleep_ms integer, retry_cap_ms integer, failover_count integer)",
+		"client integer, loop integer, retries integer, us bigint, recovery bool,"
+		"primary key(client, ts),"
+		"foreign key (client) references demo.client(client))",
 		NULL
 	};
 
@@ -383,9 +388,12 @@ demoapp_process_perform_switchover(DemoAppOptions *demoAppOptions)
 
 	if (demoAppOptions->duration <= (demoAppOptions->firstFailover + 10))
 	{
+		log_warn("Using --duration %ds and --first-failover %ds",
+				 demoAppOptions->duration,
+				 demoAppOptions->firstFailover);
 		log_error("Use a --duration of at least %ds for a failover to happen",
 				  demoAppOptions->firstFailover + 10);
-		exit(EXIT_CODE_INTERNAL_ERROR);
+		exit(EXIT_CODE_QUIT);
 	}
 
 	log_info("Failover client is started, will failover in %ds "