RFR: 8274524: SSLSocket.close() hangs if it is called during the ssl handshake

[Alexey Bakhtin]

Please review the patch for JDK-8274524

The fix just adds locks around InputStream read and skip operations to prevent concurrent read from socket.
sun/security/ssl jtreg tests passed
api/javax_net/ssl/SSLSocket/setUseClientMode jck test passed

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Commit messages:
 - 8274524: SSLSocket.close() hangs if it is called during the ssl handshake

Changes: https://git.openjdk.java.net/jdk/pull/5760/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5760&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274524
  Stats: 26 lines in 1 file changed: 17 ins; 0 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5760.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5760/head:pull/5760

PR: https://git.openjdk.java.net/jdk/pull/5760