vbdmectics may not exist after host reboot
CLOUDSTACK-6199:  Hide action events for Vm/Volume commands when the resources have display flag=0.
Introduce generic BaseAsync(Vm/Volume)Cmd to make get the flag value for logging action events.
Rename the db field as display rather than display_event in keeping with the convention
only ping timeout trigger host HA, otherwise there may be two threads try to HA the same VM