RFR: 8264975: java/net/DatagramSocket/DatagramSocketMulticasting.java fails infrequently

[Daniel Fuchs]

Please find below a fix that will make `java/net/DatagramSocket/DatagramSocketMulticasting.java` more resilient to the rare case where addresses bound to a network interfaces are updated while the test is running.

Instead of using `NetworkInterface::equals` to compare network interfaces, the test now use `NetworkConfiguration::isSameInterface` which only looks at the network interface name and index and ignore the addresses which are bound to it.

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Commit messages:
 - 8264975: java/net/DatagramSocket/DatagramSocketMulticasting.java fails infrequently

Changes: https://git.openjdk.java.net/jdk/pull/4313/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4313&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264975
  Stats: 36 lines in 3 files changed: 32 ins; 2 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4313.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4313/head:pull/4313

PR: https://git.openjdk.java.net/jdk/pull/4313