Pinned paramiko to 2.7.2 since it failed to authenticate via ssh

The Tempest tests failed to connect to VMs by Floating IPs since
the authentication to VMs failed. Maybe this is related to
https://github.com/paramiko/paramiko/issues/1984

PROD: PROD-36791
Change-Id: Ib29bf300c2b8381a303208dc40d8e78924671806
(cherry picked from commit 36b393589b99067e87a6a97fd62a41d77bbd5d3d)
2 files changed