Refactor test cases for live-migrate error case
Refactor test cases for live-migrate error case

There are a few of exceptions can be raised from live-migrate
function in conductor, this patch added some cases for
more exceptions handling and refactors the util function
with mock.

Change-Id: I6b225756efcc17bdcd6402606287c35464a3c1d0
Related-Bug: 1435633

noironetworks/nova,nikesh-mahalka/nova,openstack/nova,rahulunair/nova,MountainWei/nova,raildo/nova,cernops/nova,fnordahl/nova,BeyondTheClouds/nova,JianyuWang/nova,hanlind/nova,j-carpentier/nova,gooddata/openstack-nova,cloudbase/nova,zhimin711/nova,gooddata/openstack-nova,vmturbo/nova,jianghuaw/nova,TwinkleChawla/nova,rajalokan/nova,Francis-Liu/animated-broccoli,raildo/nova,sebrandon1/nova,phenoxim/nova,nikesh-mahalka/nova,mikalstill/nova,NeCTAR-RC/nova,zhimin711/nova,ted-gould/nova,rajalokan/nova,phenoxim/nova,gooddata/openstack-nova,felixma/nova,klmitch/nova,klmitch/nova,isyippee/nova,gooddata/openstack-nova,hanlind/nova,alaski/nova,scripnichenko/nova,jianghuaw/nova,yosshy/nova,mahak/nova,scripnichenko/nova,klmitch/nova,rajalokan/nova,hanlind/nova,CEG-FYP-OpenStack/scheduler,yosshy/nova,cyx1231st/nova,edulramirez/nova,CCI-MOC/nova,Francis-Liu/animated-broccoli,Juniper/nova,isyippee/nova,CEG-FYP-OpenStack/scheduler,devendermishrajio/nova,alaski/nova,TwinkleChawla/nova,apporc/nova,felixma/nova,apporc/nova,NeCTAR-RC/nova,devendermishrajio/nova,sebrandon1/nova,MountainWei/nova,Juniper/nova,cernops/nova,vmturbo/nova,mikalstill/nova,mikalstill/nova,dims/nova,openstack/nova,JianyuWang/nova,vmturbo/nova,cloudbase/nova,klmitch/nova,cloudbase/nova,cyx1231st/nova,bigswitch/nova,jianghuaw/nova,edulramirez/nova,vmturbo/nova,Juniper/nova,jianghuaw/nova,sebrandon1/nova,bigswitch/nova,BeyondTheClouds/nova,mahak/nova,rahulunair/nova,BeyondTheClouds/nova,mahak/nova,j-carpentier/nova,noironetworks/nova,openstack/nova,Juniper/nova,fnordahl/nova,dims/nova,rahulunair/nova,ted-gould/nova,cernops/nova,rajalokan/nova,CCI-MOC/nova