Add log for instance without host field set
Add log for instance without host field set

when doing bug debug, found some instances deleted in
api layer with DELETE call while no rpc message found in
compute layer, originally thought it's because rpc message
lost, finally found instance don't have instance.host field
set, so add this log to help further debug and better info

Change-Id: Ic92f9a25d45831c2c33a2dbe82538df218084a29

Juniper/nova,rahulunair/nova,mahak/nova,rajalokan/nova,openstack/nova,jianghuaw/nova,jianghuaw/nova,openstack/nova,sebrandon1/nova,jianghuaw/nova,vmturbo/nova,alaski/nova,vmturbo/nova,hanlind/nova,Juniper/nova,gooddata/openstack-nova,alaski/nova,Juniper/nova,jianghuaw/nova,rajalokan/nova,vmturbo/nova,gooddata/openstack-nova,mikalstill/nova,rahulunair/nova,klmitch/nova,sebrandon1/nova,cloudbase/nova,mikalstill/nova,klmitch/nova,phenoxim/nova,gooddata/openstack-nova,mahak/nova,mahak/nova,cloudbase/nova,phenoxim/nova,openstack/nova,klmitch/nova,mikalstill/nova,vmturbo/nova,rajalokan/nova,rajalokan/nova,sebrandon1/nova,hanlind/nova,gooddata/openstack-nova,cloudbase/nova,klmitch/nova,hanlind/nova,rahulunair/nova,Juniper/nova