RFR: 8238274: (sctp) JDK-7118373 is not fixed for SctpChannel

[Masanori Yano]

Please review this change to the Unix implementations of sun.nio.ch.sctp.Sctp*ChannelImpl#implCloseSelectableChannel() 
to be same as SocketChannelImpl at JDK-7118373. (The preClose is missing a check for the ST_KILLED state.)

-------------

Commit messages:
 - 8238274: (sctp) JDK-7118373 is not fixed for SctpChannel

Changes: https://git.openjdk.java.net/jdk/pull/5274/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5274&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8238274
  Stats: 213 lines in 4 files changed: 210 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5274.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5274/head:pull/5274

PR: https://git.openjdk.java.net/jdk/pull/5274