Fix broken local DB test

Committing transactions DOES help, who could have foreseen this.

Also: expose the PostgreSQL port 5432 to local 15432 via docker-compose
file. Please point me to a cleaner solution, as that port-mapping is clearly not
required except for testing.

Signed-off-by: Maximilian Seifert <max.seifert@drglitch.net>

docker/docker-compose.yml

@@ -158,6 +158,8 @@ services:
       POSTGRES_USER: dendrite
     networks:
       - internal
+    ports:
+      - "15432:5432"
 
   zookeeper:
     container_name: dendrite_zk

syncapi/storage/output_room_events_table_test.go

@@ -73,6 +73,7 @@ func Test_sanityCheckOutputRoomEvents(t *testing.T) {
 func TestSyncServerDatasource_selectEventsWithEventIDs(t *testing.T) {
 	db, err := NewSyncServerDatasource(dataSource)
 	assert.Nil(t, err)
+	truncateTable(t, db)
 	insertTestEvent(t, db)
 	ctx := context.Background()
 	txn, err := db.db.Begin()
@@ -85,6 +86,9 @@ func TestSyncServerDatasource_selectEventsWithEventIDs(t *testing.T) {
 	assert.Condition(t, func() bool {
 		return len(events) > 0
 	})
+
+	err = txn.Commit()
+	assert.Nil(t, err)
 }
 
 func insertTestEvent(t *testing.T, db *SyncServerDatasource) {