Updating the paramiko version to 2.7.0 or greater

We have recently observed that ssh-keygen by default
create OPENSSH format for keys and paramiko got the
support for decrypting it from paramiko 2.7.0[1]

We have recenlty seen failures in whitebox plugin but
considering this can also be observe in tempest as well
it's good to update the version here too.

[1]: http://www.paramiko.org/changelog.html

Change-Id: I3603bbc9787e99fe864a4ec63d49fea6b90a45a8
1 file changed