support snapshot when instance in pause,stop etc state

http://extbasicopstackcilog01.podc.sl.edst.ibm.com/test_logs/jenkins-check-nova-master-17773/logs/n-cpu.log_white.html

2018-05-03 09:06:11.450 10351 DEBUG oslo_service.periodic_task [req-5c6a3fde-2a1c-409b-9d0b-62f2bd7a4d4a tempest-ServersAdminTestJSON-386914806 tempest-ServersAdminTestJSON-386914806] Running periodic task ComputeManager._poll_rebooting_instances {{(pid=10351) run_periodic_tasks /usr/local/lib/python2.7/dist-packages/oslo_service/periodic_task.py:215}}
2018-05-03 09:06:11.452 10351 DEBUG nova.compute.manager [req-5c6a3fde-2a1c-409b-9d0b-62f2bd7a4d4a tempest-ServersAdminTestJSON-386914806 tempest-ServersAdminTestJSON-386914806] [instance: e415de96-6771-423a-9bc8-f4941de2e8a9] Start destroying the instance on the hypervisor. {{(pid=10351) _shutdown_instance /opt/stack/new/nova/nova/compute/manager.py:2347}}
2018-05-03 09:06:12.925 10351 ERROR nova.virt.zvm.utils [req-5c6a3fde-2a1c-409b-9d0b-62f2bd7a4d4a tempest-ServersAdminTestJSON-386914806 tempest-ServersAdminTestJSON-386914806] zVM Cloud Connector request guest_capture failed with parameters: ('KEX00008', u'aafe9b6e-2fce-4a0a-9335-ae85be84c799') {} . Results: {u'rs': 5, u'overallRC': 300, u'modID': 10, u'rc': 300, u'output': u'', u'errmsg': u'Failed to capture userid KEX00008 to generate image, error: The vm KEX00008 is powered off, please start up it before capture'}

this lead to some tempest failure also some feature limitation