RFR: 8154454: Fix compilation issue in PlainSocketImpl

[Claes Redestad]

Hi,

a small omission in JDK-8154238 cause Windows builds to fail. Sorry 
about that, see patch to fix this below (I was 100% certain I had run this
through JPRT last week)

Bug: https://bugs.openjdk.java.net/browse/JDK-8154454

Thanks!

/Claes

diff -r 3459ee432728 
src/java.base/windows/classes/java/net/PlainSocketImpl.java
--- a/src/java.base/windows/classes/java/net/PlainSocketImpl.java  Mon 
Apr 18 14:01:03 2016 +0200
+++ b/src/java.base/windows/classes/java/net/PlainSocketImpl.java  Mon 
Apr 18 16:35:03 2016 +0200
@@ -80,7 +80,7 @@
       * Constructs an instance with the given file descriptor.
       */
      PlainSocketImpl(FileDescriptor fd) {
-        if (useDualStackImpl) {
+        if (!preferIPv4Stack) {
              impl = new DualStackPlainSocketImpl(fd, exclusiveBind);
          } else {
              impl = new TwoStacksPlainSocketImpl(fd, exclusiveBind);