host monitor by consul

Currently, Masakari host monitor uses pacemaker and pacemaker-remote to
monitor hosts' connection. Actually, it is monitoring the hosts heartbeat
through management interface. Once a host's management interface is
detected disconnected, it will send notification to masakari to do host
recovery.

This solution is imprecise. When management interface disconnected but
tenant and storage interface connected, it means the instances on the host
can't be managed by adminitrator but they are still available to end users.

This introduces a new host monitor; specifically, host heartbeat
monitoring via management, tenant and storage interfaces by consul agent.
Only in the case of defined states, it will trigger host recovery， such as
storage interface disconnected.