Remove common/ssh.py due to migration to tempest_lib

common ssh.py module and it tests was migrated to tempest_lib.
and included in tempest-lib release 0.5.0. This commit removes
the tempest copies of this module and switches over to using
the tempest-lib copy.

Change-Id: I4a38bd16b5568ce508623170eea186a3c53f1c89
6 files changed