Fix failing tests

[jsstevenson]

Describe the bug
As of #176, three test modules fail:

• test_eutils_xmlfacades_dbsnp.py
• test_eutils_xmlfaces_esearchresult.py
• test_eutils_xmlfacades_gi.py

To Reproduce

make test

Expected behavior
They should probably be passing with minimal interventions.

Additional context
The equivalent eutils response to the dbSNP test doesn't really look like what the XML facade seems to expect. I suspect the facade might need to be updated.