Use lxml to render EC2 response
Use lxml to render EC2 response

Currently etree is a preferred library to work with xml. lxml
implementation is used for doing that in OpenStack.

Change-Id: I93ce6d1a4e8e59c70e74aa6634cdc8bc67cc5914

hayderimran7/ec2-api,stackforge/ec2-api,openstack/ec2-api,hayderimran7/ec2-api,stackforge/ec2-api,openstack/ec2-api