ENT-3187 Check that we're not calling toList on concurrent collections (#4828)

* ENT-3165 Kotlin toList() does not work on concurrent collections.  OS backport.

ENT-3165 Added comment.

* ENT-3187 Additional use of toList() on concurrent data structure.

node-api/src/main/kotlin/net/corda/nodeapi/internal/persistence/CordaPersistence.kt

@@ -163,7 +163,8 @@ class CordaPersistence(
     }
 
     fun onAllOpenTransactionsClosed(callback: () -> Unit) {
-        val allOpen = liveTransactions.values.toList()
+        // Does not use kotlin toList() as that is not safe to use on concurrent collections.
+        val allOpen = ArrayList(liveTransactions.values)
         if (allOpen.isEmpty()) {
             callback()
         } else {