JDK 9 RFR of JDK-8079651: (dc) Promiscuous.java fails with NumberFormatException due to network interference

[Amy Lu]

java/nio/channels/DatagramChannel/Promiscuous.java

This test has the same issue as JDK-8076644 [1], similar patch applied 
to this test to resolve two issues:
1. Test should attempt to reconstruct the String message with the same 
charset as is used to convert the original message to bytes, UTF-8.
2. Test should ignore data that cannot be parsed, possible there is 
interference on the network, then continue to try to read the expected id.

bug: https://bugs.openjdk.java.net/browse/JDK-8079651
webrev: http://cr.openjdk.java.net/~amlu/8079651/webrev.00/

Thanks,
Amy

[1] https://bugs.openjdk.java.net/browse/JDK-8076644