dovetail: create file pod.yaml for running HA test cases

dovetail: create file pod.yaml for running HA test cases

JIRA: DOVETAIL-407

1. HA test cases need a file pod.yaml giving the info of the pod
   (node's ip, username, password/key_file).
2. Dovetail client has finished the adaption JIRA: DOVETAIL-405.
3. CI uses create_pod_file.py to generate /home/opnfv/dovetail/userconfig/pod.yaml
4. If INSTALLER_TYPE is fuel, fetch it's jumpserver key to
   /home/opnfv/dovetail/userconfig/id_rsa

Change-Id: Iaf6afbdfb8e4331ae9a10ea3df060c37e9010a0a
Signed-off-by: xudan <xudan16@huawei.com>