objects: Don't import CellMapping from the objects module
objects: Don't import CellMapping from the objects module

We should be importing other objects from their own modules inside
modules defining objects, not from the top nova.objects module, as the
objects are only added as attributes on it after being imported.

Change-Id: I8a304807f92a005f73631fac28ba56f1e9d94b27

rajalokan/nova,NeCTAR-RC/nova,ted-gould/nova,scripnichenko/nova,j-carpentier/nova,TwinkleChawla/nova,mahak/nova,BeyondTheClouds/nova,zaina/nova,gooddata/openstack-nova,nikesh-mahalka/nova,LoHChina/nova,jianghuaw/nova,BeyondTheClouds/nova,takeshineshiro/nova,jianghuaw/nova,isyippee/nova,CCI-MOC/nova,jianghuaw/nova,klmitch/nova,cyx1231st/nova,Juniper/nova,noironetworks/nova,Francis-Liu/animated-broccoli,sebrandon1/nova,cloudbase/nova,JianyuWang/nova,mmnelemane/nova,Juniper/nova,rahulunair/nova,watonyweng/nova,barnsnake351/nova,cernops/nova,isyippee/nova,sebrandon1/nova,dims/nova,shail2810/nova,cernops/nova,bigswitch/nova,cernops/nova,MountainWei/nova,mikalstill/nova,bigswitch/nova,dims/nova,iuliat/nova,JianyuWang/nova,klmitch/nova,whitepages/nova,zaina/nova,rahulunair/nova,zhimin711/nova,JioCloud/nova_test_latest,shail2810/nova,mikalstill/nova,devendermishrajio/nova_test_latest,JioCloud/nova_test_latest,mahak/nova,openstack/nova,rajalokan/nova,TwinkleChawla/nova,openstack/nova,j-carpentier/nova,hanlind/nova,zzicewind/nova,zzicewind/nova,vmturbo/nova,mmnelemane/nova,akash1808/nova_test_latest,apporc/nova,scripnichenko/nova,gooddata/openstack-nova,akash1808/nova_test_latest,klmitch/nova,sebrandon1/nova,barnsnake351/nova,fnordahl/nova,iuliat/nova,gooddata/openstack-nova,gooddata/openstack-nova,nikesh-mahalka/nova,jianghuaw/nova,cloudbase/nova,ruslanloman/nova,phenoxim/nova,mahak/nova,NeCTAR-RC/nova,LoHChina/nova,rajalokan/nova,vmturbo/nova,yosshy/nova,raildo/nova,hanlind/nova,vmturbo/nova,watonyweng/nova,Francis-Liu/animated-broccoli,cyx1231st/nova,rajalokan/nova,hanlind/nova,raildo/nova,ted-gould/nova,CEG-FYP-OpenStack/scheduler,varunarya10/nova_test_latest,Juniper/nova,edulramirez/nova,takeshineshiro/nova,mikalstill/nova,vmturbo/nova,felixma/nova,devendermishrajio/nova_test_latest,devendermishrajio/nova,CEG-FYP-OpenStack/scheduler,edulramirez/nova,alaski/nova,MountainWei/nova,apporc/nova,CCI-MOC/nova,klmitch/nova,fnordahl/nova,ruslanloman/nova,cloudbase/nova,devendermishrajio/nova,phenoxim/nova,yosshy/nova,varunarya10/nova_test_latest,alaski/nova,felixma/nova,openstack/nova,noironetworks/nova,BeyondTheClouds/nova,whitepages/nova,zhimin711/nova,Juniper/nova,rahulunair/nova