This commit migrates the ssh common module from tempest. This module
provides a wrapper around paramiko to provide ssh connectivity to
a remote server for testing.
At the time of this migration commit the latest Change-Id for
the module was:
* tempest/common/ssh.py: Ia0de957b681cb924a57af98d99a9389ee234ed5b
Change-Id: Iad5ffbfe18690f1b6f178dde31a8ec0d0666c815