The 'model_save' helper added to the context.
The 'model_save' helper added to the context.

It use ctx().session and new transaction to flush/commit object.

Change-Id: Ife054786204affa43550aa9eb243e8e44d4e8fc3

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