8241786: 3 DatagramChannel tests and 2 MulticastSocket tests fail due to "SocketException: No buffer space available"

[Daniel Fuchs]

Hi,

Please find below a fix for:

8241786: 3 DatagramChannel tests and 2 MulticastSocket tests
          fail due to "SocketException: No buffer space available"
https://bugs.openjdk.java.net/browse/JDK-8241786

webrev:
http://cr.openjdk.java.net/~dfuchs/webrev_8241786/webrev.01/

The real fix is in these three files:

DefaultInterface.java (macOS): is modified to prefer interfaces
     that have non link local addresses
NetworkConfiguration.java (test lib): is modified to skip
     interfaces that have only link-local addresses (whether IPv4
     or IPv6) for multicasting.
MulticastSocket/SetOutgoingIf.java: this test does its own thing,
     and is modified similarly to NetworkConfiguration

Additional cleanup:

The other tests are just modified to add diagnostic and use 
try-with-resources whenever possible, and also use /othervm to avoid 
some undesirable side effects (like not seeing any trace):

MulticastSocket/SetLoopbackMode.java
MulticastSocket/SetLoopbackModeIPv4.java
DatagramChannel/AdaptorMulticasting.java
DatagramChannel/MulticastSendReceiveTests.java
DatagramChannel/Promiscuous.java

best regards,

-- daniel