catching "service resource not found" exception in create_entity

create_entity tries to fetch an entity prior to creating one.
This might raise an UG_401_Unauthorized exception which is not caught though it is to be expected.
Now it is okay to save the new entity if the exception message equals 'org.apache.usergrid.services.exceptions.ServiceResourceNotFoundException' (are there any constants for that?), any other types of exceptions will be thrown on.