Add shelve and unshelve info into devref doc
Add shelve and unshelve info into devref doc

The diagram on http://docs.openstack.org/developer/nova/devref/vmstates.html
does not currently show the "SHELVED_OFFLOADED" state and the
associated "shelve", "shelveOffload" and "unshelve" state transitions.

Change-Id: I50eb07a84336160b8120ca294598576eeb982d28
Closes-Bug: #1394215

varunarya10/nova_test_latest,openstack/nova,projectcalico/calico-nova,NeCTAR-RC/nova,edulramirez/nova,nikesh-mahalka/nova,CCI-MOC/nova,nikesh-mahalka/nova,affo/nova,gooddata/openstack-nova,devendermishrajio/nova,yosshy/nova,devendermishrajio/nova_test_latest,belmiromoreira/nova,Yusuke1987/openstack_template,bgxavier/nova,fnordahl/nova,LoHChina/nova,akash1808/nova_test_latest,orbitfp7/nova,mahak/nova,orbitfp7/nova,akash1808/nova,alexandrucoman/vbox-nova-driver,tealover/nova,thomasem/nova,barnsnake351/nova,Juniper/nova,gooddata/openstack-nova,Juniper/nova,Francis-Liu/animated-broccoli,dawnpower/nova,Tehsmash/nova,vmturbo/nova,hanlind/nova,Stavitsky/nova,eonpatapon/nova,iuliat/nova,tudorvio/nova,mikalstill/nova,ted-gould/nova,dims/nova,zaina/nova,mgagne/nova,adelina-t/nova,petrutlucian94/nova,whitepages/nova,Tehsmash/nova,JianyuWang/nova,cernops/nova,Metaswitch/calico-nova,alvarolopez/nova,zhimin711/nova,dawnpower/nova,cyx1231st/nova,NeCTAR-RC/nova,yatinkumbhare/openstack-nova,mmnelemane/nova,varunarya10/nova_test_latest,ruslanloman/nova,akash1808/nova_test_latest,silenceli/nova,gooddata/openstack-nova,joker946/nova,vmturbo/nova,hanlind/nova,tangfeixiong/nova,cloudbase/nova,openstack/nova,cernops/nova,CCI-MOC/nova,whitepages/nova,tangfeixiong/nova,scripnichenko/nova,Francis-Liu/animated-broccoli,cyx1231st/nova,cloudbase/nova,scripnichenko/nova,JioCloud/nova_test_latest,TwinkleChawla/nova,BeyondTheClouds/nova,projectcalico/calico-nova,adelina-t/nova,phenoxim/nova,cloudbase/nova-virtualbox,TwinkleChawla/nova,ruslanloman/nova,phenoxim/nova,klmitch/nova,bigswitch/nova,shail2810/nova,zhimin711/nova,BeyondTheClouds/nova,cernops/nova,hanlind/nova,jeffrey4l/nova,JioCloud/nova_test_latest,mahak/nova,vmturbo/nova,double12gzh/nova,cloudbase/nova,affo/nova,rahulunair/nova,alaski/nova,barnsnake351/nova,MountainWei/nova,edulramirez/nova,felixma/nova,mmnelemane/nova,eonpatapon/nova,shail2810/nova,MountainWei/nova,mandeepdhami/nova,noironetworks/nova,dims/nova,noironetworks/nova,mikalstill/nova,raildo/nova,belmiromoreira/nova,blueboxgroup/nova,bigswitch/nova,JioCloud/nova,jianghuaw/nova,thomasem/nova,petrutlucian94/nova,isyippee/nova,yosshy/nova,CEG-FYP-OpenStack/scheduler,BeyondTheClouds/nova,felixma/nova,silenceli/nova,rajalokan/nova,JioCloud/nova,yatinkumbhare/openstack-nova,j-carpentier/nova,jianghuaw/nova,apporc/nova,klmitch/nova,sebrandon1/nova,devendermishrajio/nova_test_latest,CloudServer/nova,apporc/nova,Juniper/nova,klmitch/nova,watonyweng/nova,alexandrucoman/vbox-nova-driver,bgxavier/nova,double12gzh/nova,rajalokan/nova,mahak/nova,CloudServer/nova,joker946/nova,ted-gould/nova,sebrandon1/nova,fnordahl/nova,kimjaejoong/nova,alaski/nova,rahulunair/nova,tudorvio/nova,alvarolopez/nova,takeshineshiro/nova,cloudbase/nova-virtualbox,jeffrey4l/nova,devendermishrajio/nova,CEG-FYP-OpenStack/scheduler,jianghuaw/nova,mandeepdhami/nova,LoHChina/nova,watonyweng/nova,iuliat/nova,rahulunair/nova,klmitch/nova,akash1808/nova,raildo/nova,jianghuaw/nova,zzicewind/nova,j-carpentier/nova,zzicewind/nova,Yusuke1987/openstack_template,openstack/nova,kimjaejoong/nova,rajalokan/nova,mikalstill/nova,Juniper/nova,rajalokan/nova,isyippee/nova,tealover/nova,zaina/nova,sebrandon1/nova,takeshineshiro/nova,blueboxgroup/nova,vmturbo/nova,Stavitsky/nova,gooddata/openstack-nova,Metaswitch/calico-nova,JianyuWang/nova,mgagne/nova