Rewrite the HA test case (2)

idea: refact the Monitor class in old file "monitor.py" with the base
class and sub-class.
detail:
1) the BaseMonitor is the base class of other monitor
2) each monitor run in independent process
3) there are two monitor("openstack-cmd" and "process") for the first test case
4) MonitorMgr class used to manager monitor process

JIRA: YARDSTICK-149

Change-Id: I2eede94481f740812212e6cb673d175b5f543c15
Signed-off-by: wym_libra <yimin.wang@huawei.com>