Split up test_is_volume_backed_instance() into five functions
Split up test_is_volume_backed_instance() into five functions

test_is_volume_backed_instance() actually did five tests with
different object instances and test cases.  This is split up into
five separate functions with reasonable names.

Change-Id: Iba51e48413e2744ff789c8761bc9188238deb98b

klmitch/nova,BeyondTheClouds/nova,cloudbase/nova,rajalokan/nova,bigswitch/nova,phenoxim/nova,cloudbase/nova,gooddata/openstack-nova,devendermishrajio/nova,jianghuaw/nova,sebrandon1/nova,apporc/nova,vmturbo/nova,rajalokan/nova,cernops/nova,gooddata/openstack-nova,klmitch/nova,klmitch/nova,vmturbo/nova,dims/nova,jianghuaw/nova,vmturbo/nova,alaski/nova,mahak/nova,CEG-FYP-OpenStack/scheduler,rahulunair/nova,mikalstill/nova,cernops/nova,NeCTAR-RC/nova,Juniper/nova,Juniper/nova,openstack/nova,gooddata/openstack-nova,apporc/nova,vmturbo/nova,phenoxim/nova,cyx1231st/nova,mahak/nova,hanlind/nova,zhimin711/nova,rahulunair/nova,mikalstill/nova,jianghuaw/nova,alaski/nova,hanlind/nova,CEG-FYP-OpenStack/scheduler,rahulunair/nova,BeyondTheClouds/nova,openstack/nova,devendermishrajio/nova,rajalokan/nova,cloudbase/nova,mahak/nova,bigswitch/nova,hanlind/nova,openstack/nova,klmitch/nova,Juniper/nova,rajalokan/nova,jianghuaw/nova,Juniper/nova,sebrandon1/nova,BeyondTheClouds/nova,sebrandon1/nova,cyx1231st/nova,mikalstill/nova,gooddata/openstack-nova,dims/nova,cernops/nova,NeCTAR-RC/nova,zhimin711/nova