Avoid internal error while quering plugin
Avoid internal error while quering plugin

* return None instead of NoneType error doesn't containt some property

Change-Id: Ibb5050f035a328e3dc7f9b69e20668ae0a686636

tellesnobrega/sahara,openstack/sahara,bigfootproject/sahara,zhangjunli177/sahara,bigfootproject/sahara,redhat-openstack/sahara,xme1226/sahara,xme1226/sahara,crobby/sahara,crobby/sahara,crobby/sahara,henaras/sahara,openstack/sahara,tellesnobrega/sahara,redhat-openstack/sahara,zhujzhuo/Sahara,mapr/sahara,zhujzhuo/Sahara,egafford/sahara,keedio/sahara,citrix-openstack-build/sahara,ekasitk/sahara,henaras/sahara,zhangjunli177/sahara,egafford/sahara,tellesnobrega/storm_plugin,matips/iosr-2015,keedio/sahara,esikachev/scenario,ekasitk/sahara,keedio/sahara,mapr/sahara,rnirmal/savanna,henaras/sahara,esikachev/scenario,esikachev/sahara-backup,xme1226/sahara,citrix-openstack-build/sahara,bigfootproject/sahara,redhat-openstack/sahara,zhujzhuo/Sahara,mapr/sahara,matips/iosr-2015,tellesnobrega/storm_plugin,zhangjunli177/sahara,esikachev/scenario,esikachev/sahara-backup,ekasitk/sahara,tellesnobrega/storm_plugin,matips/iosr-2015,citrix-openstack-build/sahara,rnirmal/savanna,esikachev/sahara-backup