Re-include QMUX notifications for FSDISOMsg

Commit aac64d3 results in the inability to use QMUX e.g for FSDISOMsg
messages that do not have MTI compliant with the ISO 8583 standard.

QMUX uses field 0 as mandatory. Therefore, in the FSDISOMsg messages
it is necessary to map elements that do not have to be MTI. In this
case, the m.isResponse() method can throws an ArrayIndexOutOfBoundsException.

However, this can be hot-fixed by enabling the "return-rejects" parameter
but a better solution is to include it in the code.

jpos/src/main/java/org/jpos/q2/iso/QMUX.java

@@ -197,12 +197,28 @@ public void request (ISOMsg m, long timeout, ISOResponseListener rl, Object hand
             sp.out (out, m);
         synchronized (this) { tx++; rxPending++; }
     }
+
+    protected boolean isNotifyEligible(ISOMsg msg) {
+        if (returnRejects)
+            return true;
+
+        try {
+            return msg.isResponse();
+        } catch (RuntimeException | ISOException ex) {
+            // * ArrayIndexOutOfBoundsException - It may occur for messages where
+            // MTI is not standard 4 characters (eg. FSDISOMsg), then notification is expected.
+            // * ISOException: When there is no field 0, the error should be logged
+            return true;
+        }
+    }
+
+    @Override
     public void notify (Object k, Object value) {
         Object obj = sp.inp (k);
         if (obj instanceof ISOMsg) {
             ISOMsg m = (ISOMsg) obj;
             try {
-                if (returnRejects || m.isResponse()) {
+                if (isNotifyEligible(m)) {
                     String key = getKey (m);
                     String req = key + ".req";
                     Object r = isp.inp (req);