Downgrade SSHD to 0.9.0-4-g5967cfd

Since there is no official 0.9.1 release of the SSHD yet, the
0.9.0-4-g5967cfd version was built from the 0.9.x branch and uploaded to
the Google cloud storage.

This change reverts the following Gerrit commits:

3d9c70c SSHD: Update to 0.13.0
52e4e0c Bump SSHD Mina version to 2.0.8
3921163 Don't use deprecated PGPPublicKeyRingCollection constructor
13452f4 Bump Bouncycastle version to 1.51
5f7d5a7 Update EncryptedContactStore to not use deprecated/removed methods
f69698c Update SSHD to 0.11.1-atlassian-1
67c38c8 Added global request handlers to SshDaemon
c31e17f Update sshd to 0.11.0
b9c66ea Bump SSHD version to 0.10.1 and enable nio2 backend

The reason for the downgrade (copied from the change 60161):

SSHD release 0.9 is known to be free from exhausting thread pool problem
[1]. Unfortunately 0.9 release suffers from sporadic handshake failures
[2].  The fix cannot be cleanly cherry-picked to 0.9 release. The back
port of this fix [3] is tracked under its own issue [4], was uploaded as
PR for SSHD Mina's GH repository [5] and merged recently [6].

Moreover, 0.9 suffers from "Authenticated with partial success" issue
[7]
that was fixed by [8], [9]; this patch must be applied as well.

This reverts commit dc7318b8eeda15732d4d2865fc5a7a0a68b3be15.

[1] https://issues.apache.org/jira/browse/SSHD-348
[2] https://issues.apache.org/jira/browse/SSHD-330
[3] https://git-wip-us.apache.org/repos/asf?p=mina-sshd.git;a=commit;\
h=2aed686bdb21681a421033c6ee5997e5cd8a9a83
[4] https://issues.apache.org/jira/browse/SSHD-356
[5] https://github.com/apache/mina-sshd/pull/7
[6] https://git-wip-us.apache.org/repos/asf?p=mina-sshd.git;a=commit;\
h=cc7162acf7ca89561ca57a9c68de735f17bf168b
[7] https://issues.apache.org/jira/browse/SSHD-254
[8] https://git-wip-us.apache.org/repos/asf?p=mina-sshd.git;a=commit;\
h=28a8ae258b08c6b41ab64ac25f2331168dc0415a
[9] https://gerrit-review.googlesource.com/51516

Change-Id: I889fb02c2cb1aa5df2cf8dcabace086f5094a914