Java Preferences sync bug

clients/cli/src/main/kotlin/com/jaytux/phoebench/clients/cli/PersistentStorage.kt

@@ -57,6 +57,7 @@ object PersistentStorage {
 
         override fun write(key: String, value: String) {
             prefs.put(key, value)
+            prefs.flush()
         }
 
         override fun erase(key: String) {