[VFS-542] Update Jsch from 0.1.50 to 0.1.51.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/vfs/trunk@1631374 13f79535-47bb-0310-9956-ffa450edef68
Update tests to httpcore-nio 4.3.2.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/vfs/trunk@1631380 13f79535-47bb-0310-9956-ffa450edef68
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git-svn-id: https://svn.apache.org/repos/asf/commons/proper/vfs/trunk@1631382 13f79535-47bb-0310-9956-ffa450edef68