Switch sshutils.SSH from subprocess to paramiko

Methods for executing commands/scripts and upload
files to remote host via ssh of sshutils.SSH class
were rewritten using the paramiko lib.

Related: blueprint serverdto-ssh

Change-Id: I1786d5c4d4b6e9c661ec84785dd9255ab39de4aa
Merge "Switch sshutils.SSH from subprocess to paramiko"