Fix find for resources with id_attribute

The find method had 'id' hard coded rather than using id_attribute.
The error message printed by find was not correct for resources that
do not have a resource_name, so I added the get_resource_name()
method.

Change-Id: I53965e74bd29081f3c3fa3f1da406aeb71cc2c01
Merge "Fix find for resources with id_attribute"