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].
The apt packages autoconf and g++ are removed because they are
dependencies of build-essential.
[1] https://cryptography.io/en/latest/installation/
[2] http://www.paramiko.org/installing.html
Change-Id: Ia7e0d64214cfd5412ec236ee4bdd6a076821d258
1b4550b0b8