add option to connect to non-standard ssh port

add option to connect to non-standard ssh port

not all enviroments have port 22 enabled for SSH.

In particular for network isolation NAT and port forwarding may be used.

example pod.yaml:

nodes:
- ip: 10.2.45.145
  name: node1
  password: ''
  role: Controller
  ssh_port: 5000
  user: root
- ip: 10.2.45.145
  name: node2
  password: ''
  role: Controller
  ssh_port: 5001
  user: root
- ip: 10.2.45.145
  name: node3
  password: ''
  role: Controller
  ssh_port: 5002
  user: root

JIRA: YARDSTICK-407

Change-Id: I8f9d6e388f31d291dd15cb900d7f71f347e41ef6
Signed-off-by: Ross Brattain <ross.b.brattain@intel.com>