Add extra functinoal tests in heatclient

For now, there are several heat osc CLIs which do not have own functional tests in heatclient/tests/functional/ dir. I think it is time to add some for heatclient.

(1)The commands which have functional tests:
     openstack stack create
     openstack stack suspend
     openstack stack resume
     opensatck stack snapshot create
     opensatck stack snapshot restore

(2)The commands which do not have functional tests:
      openstack stack delete
      openstack stack abandon .
      openstack stack adopt
      opensatck stack cancel
      opensatck stack check
      opensatck stack environment show
      opensatck stack event list
      opensatck stack event show
      opensatck stack failures list
      opensatck stack file list
      opensatck stack hook clear
      opensatck stack hook poll
      opensatck stack list
      opensatck stack output list
      opensatck stack output show
      opensatck stack resource list
      opensatck stack resource mark unhealthy
      opensatck stack resource metadata
      opensatck stack resource show
      opensatck stack resource signal
      opensatck stack show
      opensatck stack snapshot delete
      opensatck stack snapshot list
      opensatck stack snapshot show
      opensatck stack template show
      opensatck stack update