Handle changing PDCClient API.

I hit this in staging.  Some versions of the pdc-client library have a
different signature for PDCClient.  We need to specify these as keyword
arguments so we don't get spooky failures with accidental values.

module_build_service/pdc.py

@@ -41,7 +41,11 @@ def get_pdc_client_session(config):
     :param config: instance of module_build_service.config.Config
     :return pdc_client.PDCClient instance
     """
-    return PDCClient(config.pdc_url, config.pdc_develop, config.pdc_insecure) # hardcoded devel env
+    return PDCClient(
+        server=config.pdc_url,
+        develop=config.pdc_develop,
+        insecure=config.pdc_insecure,
+    )
 
 def get_variant_dict(data):
     """