Check instance existing before check in mapping
Check instance existing before check in mapping

The instance might be not exist during checking so
we provide a incorrect info to admin, this patch check
instance exist before check in mapping.

Closes-Bug: 1664465

Change-Id: I21a7d1effaadcbda4cfbd0a0465b984ebb484f24

gooddata/openstack-nova,gooddata/openstack-nova,rahulunair/nova,gooddata/openstack-nova,mahak/nova,vmturbo/nova,phenoxim/nova,phenoxim/nova,vmturbo/nova,mikalstill/nova,Juniper/nova,jianghuaw/nova,Juniper/nova,mahak/nova,openstack/nova,rahulunair/nova,rahulunair/nova,vmturbo/nova,klmitch/nova,mahak/nova,gooddata/openstack-nova,Juniper/nova,klmitch/nova,jianghuaw/nova,klmitch/nova,jianghuaw/nova,mikalstill/nova,Juniper/nova,jianghuaw/nova,mikalstill/nova,openstack/nova,openstack/nova,klmitch/nova,vmturbo/nova