Fix attribute error state if node not found
Fix attribute error state if node not found

Previously an attribute error would be raised now an error
message is shown that the node is not found instead.

Change-Id: Icdc673946834595a5b3f11ecf0101d65e5d65e05
Closes-bug: 1369801

Tesora/tesora-nodepool,seandst/nodepool,Tesora/tesora-nodepool,seandst/nodepool,citrix-openstack/nodepool,citrix-openstack/nodepool