Add process info to pod.yaml to specify the info of a special process

Add process info to pod.yaml to specify the info of a special process

1. Many HA test cases try to kill special processes with their name.
2. Then they check corresponding openstack services and
   the status of processes' recovery.
3. For different SUTs, the names of the processes and the hosts' names
   may be different.
4. So there is a requirement for Dovetail tool to provide one way to
   allow users to specify all the infos about process name and its host name.
5. All process infos can be added into file DOVETAIL_HOME/user_config/pod.yaml
6. The infos include 'attack_process' and 'attack_host' for each HA test cases.
7. If not given in this file, will use Yardtsick default values.

JIRA: DOVETAIL-627

Change-Id: I83cee991f72a8685080ed562597c70d73002623a
Signed-off-by: xudan <xudan16@huawei.com>