Paramiko version 2.0 has been released. It now uses the Python library
cryptography. Installing this requires additional system packages. This
commit adds in the appropriate packages required by cryptography based
on its documentation [1].
An alternative approach would have been to constrain the version of
Paramiko however the project describes the 1.x versions as relying on
insecure dependencies [2].
[1] https://cryptography.io/en/latest/installation/
[2] http://www.paramiko.org/installing.html
Change-Id: Ibda3558158f5fd57c1da05cf29e88b6075c0827e